U.S. patent number 10,852,655 [Application Number 16/331,297] was granted by the patent office on 2020-12-01 for liquid developer.
This patent grant is currently assigned to Kao Corporation. The grantee listed for this patent is Kao Corporation. Invention is credited to Akito Itoi, Nobumichi Kamiyoshi, Kunihiro Kano, Yuri Nannichi, Tatsuya Yamada.
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United States Patent |
10,852,655 |
Kamiyoshi , et al. |
December 1, 2020 |
Liquid developer
Abstract
A liquid developer containing a resin binder, a colorant, a
dispersant, and an insulating liquid, wherein the resin binder
contains a resin having an acidic group, and wherein the dispersant
contains a dispersant X having at least one basic
nitrogen-containing group selected from the group consisting of an
amino group, an imino group, a cyano group, an azo group, a diazo
group, and an azide group, and wherein a melting point of the
dispersant X is 34.degree. C. or higher; and a method for printing
a fused image using the liquid developer. The liquid developer of
the present invention is suitably used in development or the like
of latent images formed in, for example, electrophotography,
electrostatic recording method, electrostatic printing method or
the like.
Inventors: |
Kamiyoshi; Nobumichi (Wakayama,
JP), Nannichi; Yuri (Wakayama, JP), Kano;
Kunihiro (Wakayama, JP), Itoi; Akito (Wakayama,
JP), Yamada; Tatsuya (Wakayama, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Kao Corporation |
Tokyo |
N/A |
JP |
|
|
Assignee: |
Kao Corporation (Tokyo,
JP)
|
Family
ID: |
1000005215256 |
Appl.
No.: |
16/331,297 |
Filed: |
September 15, 2017 |
PCT
Filed: |
September 15, 2017 |
PCT No.: |
PCT/JP2017/033465 |
371(c)(1),(2),(4) Date: |
March 07, 2019 |
PCT
Pub. No.: |
WO2018/074124 |
PCT
Pub. Date: |
April 26, 2018 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20190354033 A1 |
Nov 21, 2019 |
|
Foreign Application Priority Data
|
|
|
|
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Oct 17, 2016 [JP] |
|
|
2016-203458 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03G
15/20 (20130101); G03G 9/131 (20130101); G03G
9/125 (20130101); G03G 15/10 (20130101); G03G
9/135 (20130101); G03G 9/132 (20130101) |
Current International
Class: |
G03G
9/135 (20060101); G03G 9/125 (20060101); G03G
15/20 (20060101); G03G 9/13 (20060101); G03G
15/10 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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8-36277 |
|
Feb 1996 |
|
JP |
|
H08-036277 |
|
Feb 1996 |
|
JP |
|
2003-195573 |
|
Jul 2003 |
|
JP |
|
2009-229608 |
|
Oct 2009 |
|
JP |
|
2010-25971 |
|
Feb 2010 |
|
JP |
|
2011-242457 |
|
Dec 2011 |
|
JP |
|
2014-092579 |
|
May 2014 |
|
JP |
|
2014-142624 |
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Aug 2014 |
|
JP |
|
2016-90843 |
|
May 2016 |
|
JP |
|
2017-54025 |
|
Mar 2017 |
|
JP |
|
2017-134137 |
|
Aug 2017 |
|
JP |
|
WO 2010/106873 |
|
Sep 2010 |
|
WO |
|
WO 2017/033772 |
|
Mar 2017 |
|
WO |
|
Other References
Translation of H08-036277. cited by examiner .
Translation of 2014-092579. cited by examiner .
International Search Report dated Oct. 17, 2017 in
PCT/JP2017/033465, 2 pages. cited by applicant.
|
Primary Examiner: Vajda; Peter L
Attorney, Agent or Firm: Oblon, McClelland, Maier &
Neustadt, L.L.P.
Claims
The invention claimed is:
1. A liquid developer comprising a resin binder, a colorant, a
dispersant, and an insulating liquid, wherein the resin binder
comprises a resin having an acidic group, wherein the dispersant
comprises a dispersant X which is a reaction product of a
polyalkyleneimine and a polypropylene having a carboxy group,
wherein a melting point of the dispersant X is 80.degree. C. or
higher and 150.degree. C. or lower.
2. The liquid developer according to claim 1, wherein the resin
having an acidic group is a polyester-based resin.
3. The liquid developer according to claim 2, wherein the
polyester-based resin is a polyester resin or a composite resin
comprising a polyester resin and a styrenic resin.
4. The liquid developer according to claim 1, wherein the
polyalkyleneimine has a number-average molecular weight of 100 or
more and 15,000 or less.
5. The liquid developer according to claim 1, wherein the boiling
point of the insulating liquid is 120.degree. C. or higher and
300.degree. C. or lower.
6. The liquid developer according to claim 1, wherein the viscosity
of the insulating liquid at 25.degree. C. is 1 mPas or more and 100
mPas or less.
7. The liquid developer according to claim 1, wherein the
insulating liquid comprises a polyisobutene.
8. The liquid developer according to claim 1, wherein the resin
having an acidic group is a modified polyester resin having a
urethane bond.
9. A method for printing a fused image on a resin film using a
liquid developer according to claim 1, wherein the resin film is a
polypropylene film.
10. A method for printing a fused image on a resin film using a
liquid developer according to claim 8, wherein the resin film is a
nylon film.
11. A method for printing a fused image on a resin film using a
liquid developer according to claim 1.
12. The method for printing a fused image according to claim 11,
wherein the resin film is a polyethylene terephthalate film.
13. The method for printing a fused image according to claim 11,
wherein the resin film is a resin film without a pretreatment with
a surface modifying agent.
14. The liquid developer according to claim 7, wherein the degree
of polymerization of the polyisobutene is 2 or more and 8 or
less.
15. The liquid developer according to claim 7, wherein the boiling
point of the polyisobutene is 120.degree. C. or higher and
300.degree. C. or lower.
16. A method for producing a liquid developer according to claim 1,
comprising: (a) melt-kneading a resin binder comprising a
polyester-based resin and a colorant, and pulverizing a kneaded
product obtained, to obtain toner particles; (b) adding a
dispersant to the toner particles obtained in (a), and dispersing
the toner particles in an insulating liquid to obtain a dispersion
of toner particles; and (c) subjecting the dispersion of toner
particles obtained in (b) to wet-milling, to obtain a liquid
developer.
17. The liquid developer according to claim 1, wherein the
polypropylene having a carboxy group comprises a maleic
anhydride-modified polypropylene.
Description
FIELD OF THE INVENTION
The present invention relates to a liquid developer usable in
development of latent images formed in, for example,
electrophotography, electrostatic recording method, electrostatic
printing method or the like, and a method for printing using the
liquid developer.
BACKGROUND OF THE INVENTION
Electrophotographic developers are a dry developer in which toner
components composed of materials containing a colorant and a resin
binder are used in a dry state, and a liquid developer in which
toner components are dispersed in an insulating liquid.
In a liquid developer, toner particles are dispersed in oil in an
insulating liquid, thereby making it possible to form smaller
particle sizes as compared to a dry developer. Therefore,
high-quality printouts can be obtained surpassing offset printing
or gravure printing, so that the liquid developer is suitable for
applications in commercial printings and industrial printings.
Patent Publication 1 discloses a liquid developer comprising a
resin binder (A), a colorant (B), a polymer dispersant (C), and a
carrier liquid (D), characterized in that the polymer dispersant
(C) is prepared by copolymerizing at least an ethylenically
unsaturated monomer having an amino group and an ethylenically
unsaturated monomer having an alkyl group having 9 to 24 carbon
atoms, and has an amine value of from 5 to 150 mgKOH/g, and that
the carrier liquid (D) is an aliphatic hydrocarbon, wherein a
proportion of a primary carbon is 55% or more, and a proportion of
a secondary carbon is 30% or less, of the total number of carbon
atoms of primary to tertiary carbons of the aliphatic
hydrocarbon.
Patent Publication 2 discloses a wet type developer comprising
toner particles at least containing one or more colorants and a
resin binder, dispersed in a carrier liquid, wherein the colorant
at least contains a pigment having a basic group, and wherein the
resin binder is a polyester resin containing an aromatic carboxylic
acid having three or more carboxyl groups in the molecule as a
monomer constituting unit.
Patent Publication 1: Japanese Patent Laid-Open No. 2016-90843
Patent Publication 2: WO 2010/106873
SUMMARY OF THE INVENTION
The present invention relates to: [1] a liquid developer containing
a resin binder, a colorant, a dispersant, and an insulating liquid,
wherein the resin binder contains a resin having an acidic group,
and wherein the dispersant contains a dispersant X having at least
one basic nitrogen-containing group selected from the group
consisting of an amino group, an imino group, a cyano group, an azo
group, a diazo group, and an azide group, a melting point of the
dispersant X is 34.degree. C. or higher; [2] a liquid developer
according to the above [1], wherein the dispersant X has a
propylene backbone; [3] a liquid developer according to the above
[1] or [2], wherein the resin having an acidic group is a modified
polyester resin having a urethane bond; [4] a method for printing a
fused image on a resin film using a liquid developer as defined in
any one of the above [1] to [3], wherein the resin film is a
polyethylene terephthalate film; [5] a method for printing a fused
image on a resin film using a liquid developer as defined in the
above [2] or [3], wherein the resin film is a polypropylene film;
and [6] a method for printing a fused image on a resin film using a
liquid developer as defined in the above [3], wherein the resin
film is a nylon film.
DETAILED DESCRIPTION OF THE INVENTION
In recent years, applications of printouts have been extended to
not only papers but also resin films made of materials such as
polyethylene terephthalate (PET), polypropylene (PP), vinyl
chloride, and nylons.
However, when a fused image is printed on a resin film, in order to
fuse toner particles, a pretreatment step of applying a surface
modification agent to a resin film has been necessitated, so that
not only larger scaled printing apparatuses and complicated systems
are required, but also the image quality may be lowered.
The present invention relates to a liquid developer which is
fusible to a resin film which is not subjected to a pretreatment
with a surface modification agent, and a method for printing using
the liquid developer.
The liquid developer of the present invention can be suitably used
also in fused image printing to a resin film which is not subjected
to a pretreatment with a surface modification agent.
The liquid developer of the present invention contains a resin
binder, a colorant, a dispersant, and an insulating liquid.
[Resin Binder]
The resin binder contains a resin having an acidic group. The resin
having an acidic group can be adsorbed by the dispersant by an
interaction with a dispersant X having a basic nitrogen-containing
group, so that the resin binder has excellent dispersion
stability.
The acidic group includes a carboxy group, a sulfo group, a
phosphate group, and the like, among which a carboxy group is
preferred, from the viewpoint of dispersion stability of the toner
particles and availability.
Therefore, it is preferable that the resin having an acidic group
is a polyester-based resin.
The polyester-based resin includes polyester resins, composite
resins containing polyester resins and other resins such as
styrenic resins, and the like. In addition, the polyester-based
resin may be a modified polyester-based resin to an extent that the
properties thereof are not substantially impaired.
In the present invention, it is preferable that the polyester resin
is a polycondensate of an alcohol component containing a dihydric
or higher polyhydric alcohol and a carboxylic acid component
containing a dicarboxylic or higher polycarboxylic acid
compound.
The dihydric alcohol includes, for example, aliphatic diols having
2 or more carbon atoms and 20 or less carbon atoms, and preferably
having 2 or more carbon atoms and 15 or less carbon atoms; an
alkylene oxide adduct of bisphenol A represented by the formula
(I):
##STR00001##
wherein RO and OR are an oxyalkylene group, wherein R is an
ethylene group and/or a propylene group; and each of x and y is a
positive number showing an average number of moles of alkylene
oxide added, wherein a value of the sum of x and y is 1 or more,
and preferably 1.5 or more, and 16 or less, preferably 8 or less,
more preferably 6 or less, and even more preferably 4 or less.
Specific examples of the diol having 2 or more carbon atoms and 20
or less carbon atoms include ethylene glycol, 1,2-propanediol,
1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, bisphenol A,
hydrogenated bisphenol A, and the like.
The alcohol component is preferably an alkylene oxide adduct of
bisphenol A represented by the formula (I) or 1,2-propanediol, from
the viewpoint of improving pulverizability of the toner, thereby
obtaining toner particles having a smaller particle size, from the
viewpoint of improving low-temperature fusing ability of the liquid
developer, and from the viewpoint of improving dispersion stability
of the toner particles, thereby improving storage stability. The
alkylene oxide adduct of bisphenol A represented by the formula (I)
is more preferred, from the viewpoint of pulverizability. Also,
1,2-propanediol is more preferred, from the viewpoint of storage
stability. The content of the alkylene oxide adduct of bisphenol A
represented by the formula (I) or 1,2-propanediol is preferably 50%
by mol or more, more preferably 70% by mol or more, even more
preferably 90% by mol or more, even more preferably 95% by mol or
more, and even more preferably 100% by mol, of the alcohol
component. When 1,2-propanediol and the alkylene oxide adduct of
bisphenol A represented by the formula (I) are used together, it is
preferable that a total content of both is within the above
range.
The trihydric or higher polyhydric alcohol includes trihydric or
higher polyhydric alcohols having 3 or more carbon atoms and 20 or
less carbon atoms, and preferably having 3 or more carbon atoms and
10 or less carbon atoms. Specific examples include sorbitol,
1,4-sorbitan, pentaerythritol, glycerol, trimethylolpropane, and
the like.
The dicarboxylic acid compound includes, for example, dicarboxylic
acids having 3 or more carbon atoms and 30 or less carbon atoms,
preferably having 3 or more carbon atoms and 20 or less carbon
atoms, and more preferably having 3 or more carbon atoms and 10 or
less carbon atoms, or anhydrides thereof, derivatives thereof such
as alkyl esters of which alkyl has 1 or more carbon atoms and 3 or
less carbon atoms, and the like. Specific examples include aromatic
dicarboxylic acids such as phthalic acid, isophthalic acid, and
terephthalic acid; and aliphatic dicarboxylic acids such as fumaric
acid, maleic acid, succinic acid, glutaric acid, adipic acid,
sebacic acid, and succinic acid substituted with an alkyl group
having 1 or more carbon atoms and 20 or less carbon atoms or with
an alkenyl group having 2 or more carbon atoms and 20 or less
carbon atoms.
The carboxylic acid component is preferably terephthalic acid
and/or fumaric acid, and more preferably terephthalic acid, from
the viewpoint of improving low-temperature fusing ability of the
toner, and from the viewpoint of improving dispersion stability of
the toner particles, thereby improving storage stability. The
content of the terephthalic acid or fumaric acid or a total content
of terephthalic acid and fumaric acid is preferably 40% by mol or
more, more preferably 50% by mol or more, even more preferably 70%
by mol or more, even more preferably 90% by mol or more, even more
preferably 95% by mol or more, and even more preferably 100% by
mol, of the carboxylic acid component.
The tricarboxylic or higher polycarboxylic acid compound includes,
for example, tricarboxylic or higher polycarboxylic acids having 4
or more carbon atoms and 20 or less carbon atoms, preferably having
6 or more carbon atoms and 20 or less carbon atoms, more preferably
having 7 or more carbon atoms and 15 or less carbon atoms, even
more preferably having 8 or more carbon atoms and 12 or less carbon
atoms, and even more preferably having 9 or more carbon atoms and
10 or less carbon atoms, or anhydrides thereof, derivatives thereof
such as alkyl esters of which alkyl has 1 or more carbon atoms and
3 or less carbon atoms and the like. Specific examples include
1,2,4-benzenetricarboxylic acid (trimellitic acid),
1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), or acid
anhydrides thereof, and the like.
The content of the tricarboxylic or higher polycarboxylic acid
compound is preferably 1% by mol or more, more preferably 2% by mol
or more, and even more preferably 3% by mol or more, and preferably
30% by mol or less, more preferably 25% by mol or less, and even
more preferably 20% by mol or less, of the carboxylic acid
component, from the viewpoint of improving hot offset resistance of
the toner and improving pulverizability of the toner particles.
Here, the alcohol component may contain a monohydric alcohol, and
the carboxylic acid component may contain a monocarboxylic acid
compound in proper amounts, from the viewpoint of adjusting a
molecular weight and a softening point of the polyester resin.
The equivalent ratio of the carboxylic acid component to the
alcohol component in the polyester resin, i.e. COOH group or
groups/OH group or groups, is preferably 0.6 or more, more
preferably 0.7 or more, and more preferably 0.75 or more, and
preferably 1.1 or less, more preferably 1.05 or less, and even more
preferably 1 or less, from the viewpoint of adjusting a softening
point of the polyester resin.
The polyester resin can be produced, for example, by polycondensing
the alcohol component and the carboxylic acid component in an inert
gas atmosphere at a temperature of 130.degree. C. or higher, and
preferably 170.degree. C. or higher, and 250.degree. C. or lower,
and preferably 240.degree. C. or lower, preferably in the presence
of an esterification catalyst, optionally in the presence of an
esterification promoter, a polymerization inhibitor or the
like.
The esterification catalyst includes tin compounds such as
dibutyltin oxide and tin(II) 2-ethylhexanoate; titanium compounds
such as titanium diisopropylate bistriethanolaminate; and the like,
and the tin compounds are preferred. The amount of the
esterification catalyst used is preferably 0.01 parts by mass or
more, and more preferably 0.1 parts by mass or more, and preferably
1.5 parts by mass or less, and more preferably 1.0 part by mass or
less, based on 100 parts by mass of a total amount of the alcohol
component and the carboxylic acid component. The esterification
promoter includes gallic acid, and the like. The amount of the
esterification promoter used is preferably 0.001 parts by mass or
more, and more preferably 0.01 parts by mass or more, and
preferably 0.5 parts by mass or less, and more preferably 0.1 parts
by mass or less, based on 100 parts by mass of a total amount of
the alcohol component and the carboxylic acid component. The
polymerization inhibitor includes t-butyl catechol, and the like.
The amount of the polymerization inhibitor used is preferably 0.001
parts by mass or more, and more preferably 0.01 parts by mass or
more, and preferably 0.5 parts by mass or less, and more preferably
0.1 parts by mass or less, based on 100 parts by mass of a total
amount of the alcohol component and the carboxylic acid
component.
Preferred modified polyester resins in the present invention
include, for example, modified polyester resins having a urethane
bond in which adhesiveness to a nylon film is excellent, i.e.
urethane-modified polyester resins.
The urethane-modified polyester resin is obtained by, for example,
synthesizing a polyester prepolymer obtained by polycondensation of
a dihydric or higher polyhydric alcohol component and a
dicarboxylic or higher polycarboxylic acid component, and
stretching the above polyester using an isocyanate compound.
The equivalent molar ratio of the carboxylic acid component to the
alcohol component used in the polyester prepolymer, i.e. OH group
or groups/COOH group or groups, is preferably 100/40 or less, more
preferably 100/55 or less, and even more preferably 100/60 or less,
and preferably 100/100 or more, more preferably 100/90 or more, and
even more preferably 100/80 or more, from the viewpoint of the
reactivity with the isocyanate.
The isocyanate forms a urethane bond by bonding with the polyester
prepolymer. This urethane bond improves adhesiveness to a nylon
film.
Isocyanates are mainly classified into alicyclic isocyanates,
aliphatic isocyanates, or aromatic isocyanates, and at least one
member from aliphatic isocyanates and alicyclic isocyanates is
preferred, from the viewpoint of reactivity and fusing ability.
The aliphatic isocyanate includes hexamethylene diisocyanate,
trimethylhexamethylene diisocyanate, lysine diisocyanate,
hexamethylene triisocyanate, and the like, among which
hexamethylene diisocyanate is preferred.
The alicyclic isocyanate includes isophorone diisocyanate,
dicyclohexylmethane diisocyanate, cyclohexane diisocyanate,
cyclohexane triisocyanate, and the like, among which isophorone
diisocyanate, dicyclohexylmethane diisocyanate, or cyclohexane
diisocyanate is preferred.
Each of the aliphatic polyisocyanates and the alicyclic
polyisocyanates mentioned above may be used alone or in a
combination of two or more kinds.
Also, it is possible to use, in addition to the aliphatic
polyisocyanate and the alicyclic polyisocyanate, an aromatic
polyisocyanate within the range that would not impair the effects
of the present invention. The aromatic polyisocyanate includes
phenylene diisocyanate, tolylene diisocyanate, diphenylmethane
diisocyanate, naphthalene diisocyanate, triphenylmethane
triisocyanate, and the like, and polyisocyanates such as xylylene
diisocyanate, tetramethyl xylylene diisocyanate, methylbenzene
triisocyanate, and the like, and these aromatic polyisocyanates may
be used alone or in a combination of two or more kinds.
The amount of the isocyanate used, based on 100 parts by mass of
the polyester, is preferably 5 parts by mass or more, and more
preferably 10 parts by mass or more, from the viewpoint of fusing
ability of the liquid developer to a nylon film, and the amount
used is preferably 100 parts by mass or less, and more preferably
50 parts by mass or less, from the viewpoint of dispersion
stability of the liquid developer.
The method for synthesizing a urethane-modified polyester resin is
not particularly limited, and the urethane-modified polyester resin
is synthesized using various known methods, reaction catalysts, and
reaction inhibitors. The urethane-modified polyester resin of the
present invention may be a solvent-soluble type or may be an
aqueous dispersible type such as a self-emulsification type or a
forced emulsification type using a dispersant.
The method for self-emulsification or forced emulsification of the
urethane-modified polyester resin is not particularly limited, and
various kinds of known methods can be employed. A preferred method
is one in which a diol having a carboxyalkyl as a side chain is
added as a raw material, thereby introducing a carboxy group into a
urethane resin to make the resin hydrophilic.
Other modified polyester resins include a polyester resin grafted
or blocked with a phenol, an epoxy or the like according to a
method described in Japanese Patent Laid-Open No. Hei-10-239903,
Hei-8-20636, or the like.
As a composite resin, a composite resin containing the above
polyester resin and a styrenic resin is preferred.
The styrenic resin is a product of addition polymerization of raw
material monomers containing at least styrene or a styrene
derivative such as .alpha.-methylstyrene or vinyltoluene
(hereinafter, the styrene and styrene derivatives are collectively
referred to as "styrenic compound").
The content of the styrenic compound, preferably styrene, in the
raw material monomers for the styrenic resin, is preferably 50% by
mass or more, more preferably 70% by mass or more, and even more
preferably 80% by mass or more, from the viewpoint of improving
dispersion stability of the toner particles, thereby improving
storage stability, and the content is preferably 95% by mass or
less, more preferably 93% by mass or less, and even more preferably
90% by mass or less, from the viewpoint of improving
low-temperature fusing ability of the toner and from the viewpoint
of improving wet milling property.
In addition, the styrenic resin may contain an alkyl (meth)acrylate
of which alkyl group has 7 or more carbon atoms as a raw material
monomer. The alkyl (meth)acrylate includes 2-ethylhexyl
(meth)acrylate, (iso)octyl (meth)acrylate, (iso)decyl
(meth)acrylate, (iso)stearyl (meth)acrylate, and the like. These
alkyl (meth)acrylates are preferably used alone or in two or more
kinds. Here, the expression "(iso)" as used herein means to embrace
both cases where these groups are present and cases where they are
absent, and in the cases where these groups are absent, they are
normal form. Also, the expression "(meth)acrylic acid" is acrylic
acid, methacrylic acid, or the both.
The number of carbon atoms of the alkyl group in the alkyl
(meth)acrylate as the raw material monomers for the styrenic resin
is preferably 7 or more, and more preferably 8 or more, from the
viewpoint of improving low-temperature fusing ability of the toner,
and the number of carbon atoms is preferably 12 or less, and more
preferably 10 or less, from the viewpoint of storage stability.
Here, the number of carbon atoms of the alkyl ester refers to the
number of carbon atoms derived from the alcohol component
constituting the ester.
The raw material monomers for styrene resins may contain raw
material monomers other than the styrenic compound and the alkyl
(meth)acrylate, including, for example, ethylenically unsaturated
monoolefins such as ethylene and propylene; diolefins such as
butadiene; halovinyls such as vinyl chloride; vinyl esters such as
vinyl acetate and vinyl propionate; ethylenically monocarboxylic
acid esters such as dimethylaminoethyl (meth)acrylate; vinyl ethers
such as vinyl methyl ether; vinylidene halides such as vinylidene
chloride; N-vinyl compounds such as N-vinylpyrrolidone; and the
like.
The addition polymerization reaction of the raw material monomers
for the styrenic resin can be carried out, for example, in the
presence of a polymerization initiator such as dicumyl peroxide, a
polymerization inhibitor, a crosslinking agent, or the like, and in
the presence of an organic solvent or in the absence of a solvent,
and the temperature conditions are preferably 110.degree. C. or
higher, and more preferably 140.degree. C. or higher, and
preferably 200.degree. C. or lower, and more preferably 170.degree.
C. or lower.
When an organic solvent is used during the addition polymerization
reaction, xylene, toluene, methyl ethyl ketone, acetone or the like
can be used. The amount of the organic solvent used is preferably
10 parts by mass or more and 50 parts by mass or less, based on 100
parts by mass of the raw material monomers for the styrenic
resin.
In the present invention, it is preferable that the composite resin
is a resin in which a polyester resin and a styrenic resin are
chemically bonded via a dually reactive monomer, which is capable
of reacting with both the raw material monomers for the polyester
resin and the raw material monomers for the styrenic resin, from
the viewpoint of dispersion stability and pulverizability of the
toner particles.
The dually reactive monomer is preferably a compound having within
its molecule at least one functional group selected from the group
consisting of a hydroxyl group, a carboxy group, an epoxy group, a
primary amino group and a secondary amino group, preferably a
hydroxyl group and/or a carboxy group, and more preferably a
carboxy group, and an ethylenically unsaturated bond, and the
dually reactive monomer is more preferably at least one member
selected from the group consisting of acrylic acid, methacrylic
acid, fumaric acid, maleic acid, and maleic anhydride, and, from
the viewpoint of reactivities of the polycondensation reaction and
addition polymerization reaction, even more preferably at least one
member selected from the group consisting of acrylic acid,
methacrylic acid, and fumaric acid. Here, in a case where the
dually reactive monomer is used together with a polymerization
inhibitor, a polycarboxylic acid compound having an ethylenically
unsaturated bond such as fumaric acid functions as a raw material
monomer for a polyester resin. In this case, fumaric acid or the
like is not a dually reactive monomer, but a raw material monomer
for a polyester resin.
In addition, the dually reactive monomer may be one or more
(meth)acrylate esters selected from acrylate esters and
methacrylate esters of which alkyl group has 6 or less carbon
atoms.
The (meth)acrylate ester is preferably an alkyl (meth)acrylate,
from the viewpoint of reactivity to transesterification, and the
alkyl group has the number of carbon atoms of preferably 2 or more,
and more preferably 3 or more, and preferably 6 or less, and more
preferably 4 or less. The alkyl group may have a substituent such
as a hydroxyl group.
Specific examples of the alkyl (meth)acrylate include methyl
(meth)acrylate, ethyl (meth)acrylate, (iso)propyl (meth)acrylate,
2-hydroxyethyl (meth)acrylate, (iso or tertiary)butyl
(meth)acrylate, hexyl (meth)acrylate, and the like. Here, the
expression "(iso or tertiary)" means to embrace both cases where
these groups are present and cases where they are absent, and in
the cases where these groups are absent, they are normal form.
In the present invention, the acrylate ester is preferably an alkyl
acrylate of which alkyl group has 2 or more carbon atoms and 6 or
less carbon atoms, and more preferably butyl acrylate, and the
methacrylate ester is preferably an alkyl methacrylate of which
alkyl group has 2 or more carbon atoms and 6 or less carbon atoms,
and more preferably butyl methacrylate.
The amount of the dually reactive monomer used, based on 100 mol of
a total of the alcohol component of the polyester resin, is
preferably 1 mol or more, and more preferably 2 mol or more, from
the viewpoint of enhancing dispersibility of the styrenic resin and
the polyester resin, thereby improving durability of the toner, and
the amount of the dually reactive monomer used is preferably 30 mol
or less, more preferably 20 mol or less, and even more preferably
10 mol or less, from the viewpoint of low-temperature fusing
temperature.
In addition, the amount of the dually reactive monomer used, based
on 100 parts by mass of a total of the raw material monomers for
the styrenic resin, is preferably 1 part by mass or more, and more
preferably 2 parts by mass or more, from the viewpoint of enhancing
dispersibility of the styrenic resin and polyester resin, thereby
improving durability of the toner, and the amount of the dually
reactive monomer used is preferably 30 parts by mass or less, more
preferably 20 parts by mass or less, and even more preferably 10
parts by mass or less, from the viewpoint of low-temperature fusing
ability. Here, a total of the raw material monomers for the
styrenic resin includes a polymerization initiator.
It is preferable that the composite resin obtained by using a
dually reactive monomer is specifically produced in accordance with
the following method. It is preferable that the dually reactive
monomer is used in the addition polymerization reaction together
with the raw material monomers for the styrenic resin, from the
viewpoint of improving durability of the toner, and from the
viewpoint of improving low-temperature fusing ability and
heat-resistant storage property of the toner.
(i) Method including the steps of (A) carrying out a
polycondensation reaction of raw material monomers for a polyester
resin; and thereafter (B) carrying out an addition polymerization
reaction of raw materials monomers for a styrenic resin and a
dually reactive monomer
In this method, the step (A) is carried out under reaction
temperature conditions appropriate for a polycondensation reaction,
a reaction temperature is then lowered, and the step (B) is carried
out under temperature conditions appropriate for an addition
polymerization reaction. It is preferable that the raw material
monomers for the styrenic resin and the dually reactive monomer are
added to a reaction system at a temperature appropriate for an
addition polymerization reaction. The dually reactive monomer also
reacts with the polyester resin as well as in the addition
polymerization reaction.
After the step (B), a reaction temperature is raised again, a raw
material monomer which is a trivalent or higher polyvalent monomer
for a polyester resin serving as a crosslinking agent is optionally
added to the reaction system, whereby the polycondensation reaction
of the step (A) and the reaction with the dually reactive monomer
can be further progressed.
(ii) Method including the steps of (B) carrying out an addition
polymerization reaction of raw material monomers for a styrenic
resin and a dually reactive monomer, and thereafter (A) carrying
out a polycondensation reaction of raw material monomers for a
polyester resin
In this method, the step (B) is carried out under reaction
temperature conditions appropriate for an addition polymerization
reaction, a reaction temperature is then raised, and the step (A) a
polycondensation reaction is carried out under temperature
conditions appropriate for the polycondensation reaction. The
dually reactive monomer is also involved in a polycondensation
reaction as well as the addition polymerization reaction.
The raw material monomers for the polyester resin may be present in
a reaction system during the addition polymerization reaction, or
the raw material monomers for the polyester resin may be added to a
reaction system under temperatures conditions appropriate for the
polycondensation reaction. In the former case, the progress of the
polycondensation reaction can be adjusted by adding an
esterification catalyst at a temperature appropriate for the
polycondensation reaction.
(iii) Method including carrying out reactions under the conditions
of concurrently progressing the step (A) a polycondensation
reaction of raw material monomers for a polyester resin and the
step (B) an addition polymerization reaction of raw materials
monomers for a styrenic resin and a dually reactive monomer
In this method, it is preferable that the steps (A) and (B) are
concurrently carried out under reaction temperature conditions
appropriate for an addition polymerization reaction, a reaction
temperature is raised, a raw material monomer which is a trivalent
or higher polyvalent monomer for the polyester resin serving as a
crosslinking agent is optionally added to a polymerization system
under temperature conditions appropriate for a polycondensation
reaction, and the polycondensation reaction of the step (A) is
further carried out. During the process, the polycondensation
reaction alone can also be progressed by adding a radical
polymerization inhibitor under temperature conditions appropriate
for the polycondensation reaction. The dually reactive monomer is
also involved in a polycondensation reaction as well as the
addition polymerization reaction.
In the above method (i), a polycondensation resin that is
previously polymerized may be used in place of the step (A)
carrying out a polycondensation reaction. In the above method
(iii), when the steps (A) and (B) are concurrently progressed, a
mixture containing raw material monomers for the styrenic resin can
be added dropwise to a mixture containing raw material monomers for
the polyester resin to react.
It is preferable that the above methods (i) to (iii) are carried
out in a single vessel.
The mass ratio of the styrenic resin to the polyester resin in the
composite resin, i.e. styrenic resin/polyester resin, is preferably
3/97 or more, more preferably 7/93 or more, and even more
preferably 10/90 or more, from the viewpoint of pulverizability of
the toner particles, and the mass ratio is preferably 45/55 or
less, more preferably 40/60 or less, even more preferably 35/65 or
less, even more preferably 30/70 or less, and even more preferably
25/75 or less, from the viewpoint of dispersion stability of the
toner particles. Here, in the above calculation, the mass of the
polyester resin is an amount in which the amount of reaction water
(calculated value) dehydrated by the polycondensation reaction is
subtracted from the mass of the raw material monomers for the
usable polyester resin, and the amount of the dually reactive
monomer is included in the amount of the raw material monomers for
the polyester resin. Also, the mass of the styrenic resin is a
total amount of the raw material monomers for the styrenic resin
and the polymerization initiator.
The softening point of the polyester-based resin is preferably
70.degree. C. or higher, and more preferably 75.degree. C. or
higher, from the viewpoint of improving dispersion stability of the
toner particles, thereby improving storage stability, and the
softening point is preferably 160.degree. C. or lower, more
preferably 130.degree. C. or lower, even more preferably
120.degree. C. or lower, and even more preferably 110.degree. C. or
lower, from the viewpoint of improving low-temperature fusing
ability of the liquid developer.
The glass transition temperature of the polyester-based resin is
preferably 40.degree. C. or higher, and more preferably 45.degree.
C. or higher, from the viewpoint of improving dispersion stability
of the toner particles, thereby improving storage stability, and
the glass transition temperature is preferably 80.degree. C. or
lower, more preferably 70.degree. C. or lower, and even more
preferably 60.degree. C. or lower, from the viewpoint of improving
low-temperature fusing ability.
The acid value of the polyester-based resin is preferably 3 mgKOH/g
or more, more preferably 5 mgKOH/g or more, and even more
preferably 8 mgKOH/g or more, and preferably 60 mgKOH/g or less,
more preferably 50 mgKOH/g or less, even more preferably 40 mgKOH/g
or less, and even more preferably 30 mgKOH/g or less, from the
viewpoint of reducing viscosity of the liquid developer, and from
the viewpoint of improving dispersion stability of the toner
particles, thereby improving storage stability. The acid value of
the polyester-based resin can be adjusted by a method such as
varying an equivalent ratio of the carboxylic acid component to the
alcohol component, varying a reaction time during the production of
the resin, or varying the content of the tricarboxylic or higher
polycarboxylic acid compound.
The content of the polyester-based resin in the resin binder is
preferably 90% by mass or more, more preferably 95% by mass or
more, and even more preferably 100% by mass, i.e. only the
polyester-based resin is used. However, other resin besides the
polyester-based resin may be contained within the range that would
not impair the effects of the present invention. The resins besides
the polyester-based resin include, for example, one or more members
selected from resins such as styrenic resins which are homopolymers
or copolymers containing styrene or styrene substitutes, such as
polystyrenes, styrene-propylene copolymers, styrene-butadiene
copolymers, styrene-vinyl chloride copolymers, styrene-vinyl
acetate copolymers, styrene-maleic acid copolymers,
styrene-acrylate ester copolymers, and styrene-methacrylate ester
copolymers, epoxy resins, rosin-modified maleic acid resins,
polyethylene-based resins, polypropylene-based resins,
polyurethane-based resins, silicone resins, phenol resins, and
aliphatic or alicyclic hydrocarbon resins.
[Colorant]
As the colorant, dyes, pigments and the like which are used as
colorants for toners can be used. Examples include carbon blacks,
Phthalocyanine Blue, Permanent Brown FG, Brilliant Fast Scarlet,
Pigment Green B, Rhodamine-B Base, Solvent Red 49, Solvent Red 146,
Solvent Blue 35, quinacridone, carmine 6B, isoindoline, disazo
yellow, and the like. In the present invention, the toner particles
may be any one of black toners and color toners.
The content of the colorant is preferably 5 parts by mass or more,
more preferably 10 parts by mass or more, and even more preferably
15 parts by mass or more, based on 100 parts by mass of the resin
binder, from the viewpoint of improving optical density, and the
content is preferably 100 parts by mass or less, more preferably 70
parts by mass or less, even more preferably 50 parts by mass or
less, and even more preferably 25 parts by mass or less, based on
100 parts by mass of the resin binder, from the viewpoint of
improving pulverizability of the toner, thereby forming smaller
particle sizes, from the viewpoint of improving low-temperature
fusing ability, and from the viewpoint of improving dispersion
stability of the toner particles, thereby improving storage
stability.
[Dispersant]
Since the dispersant in the present invention contains a dispersant
X having a basic nitrogen-containing group having a melting point
of a given temperature or higher, the dispersant can be suitably
used in fused image printing to a resin film which is not subjected
to a pretreatment with a surface modification agent. The reasons
therefor are not necessarily certain, and they are assumed to be as
follows. In the present invention, a dispersant X acts as an
adhesive for fusing toner particles on a resin film. A film surface
is modified by localizing a dispersant on an interface of a film
and toner particles, so that the dispersant is strongly adsorbed to
the toner via an adsorbing group having a strong basicity, thereby
firmly adhering a fused image on the film. By using a dispersant
having a melting point of a given temperature or higher, a fused
image becomes even firmer.
The basic nitrogen-containing group is at least one member selected
from the group consisting of amino groups (--NH.sub.2, --NHR,
--NHRR'), an imino group (.dbd.NH), a cyano group (--CN), an azo
group (--N.dbd.N--), a diazo group (.dbd.N.sub.2), and an azide
group (--N.sub.3). Here, each of R and R' stands for a hydrocarbon
group having from 1 to 5 carbon atoms. The imino group and/or amino
groups are preferred, from the viewpoint of adsorbability of the
dispersant to the toner particles, and the imino group is more
preferred, from the viewpoint of availability. Here, although an
amide group is a basic group, its basicity is very weak, so that
the interactions with a resin having an acidic group are extremely
weak, thereby completely not acting as an adhesive to a film.
The functional group contained besides the basic
nitrogen-containing group includes, for example, a hydroxy group, a
formyl group, an acetal group, an oxime group, a thiol group, and
the like.
The proportion of the basic nitrogen-containing group occupying the
dispersant X, as calculated in terms of the number of heteroatoms,
is preferably 70% by number or more, more preferably 80% by number
or more, even more preferably 90% by number or more, even more
preferably 95% by number or more, and even more preferably 100% by
number, from the viewpoint of dispersion stability and adhesiveness
to a film.
It is preferable that the dispersant X contains a hydrocarbon
having 16 or more carbon atoms, a hydrocarbon having 16 or more
carbon atoms partly substituted with a halogen atom, a hydrocarbon
having 16 or more carbon atoms having a reactive functional group,
a polymer of a hydroxycarboxylic acid having 16 or more carbon
atoms, a polymer obtained from a dibasic acid having 2 or more
carbon atoms and 22 or less carbon atoms and a diol having 2 or
more carbon atoms and 22 or less carbon atoms, a polymer of an
alkyl (meth)acrylate having 16 or more carbon atoms, or a group
derived from a polyolefin (hereinafter also referred to as
"dispersible group"), from the viewpoint of dispersibility of the
liquid developer.
The hydrocarbon having 16 or more carbon atoms is preferably a
hydrocarbon having 16 or more carbon atoms and 24 or less carbon
atoms, which includes, for example, hexadecene, octadecene,
eicosane, docosane, and the like.
The hydrocarbon having 16 or more carbon atoms partly substituted
with a halogen atom is preferably a hydrocarbon having 16 or more
carbon atoms and 24 or less carbon atoms partly substituted with a
halogen atom, which includes, for example, chlorohexadecane,
bromohexadecane, chlorooctadecane, bromooctadecane, chloroeicosane,
bromoeicosane, chlorodocosane, bromodocosane, and the like.
The hydrocarbon having 16 or more carbon atoms having a reactive
functional group is preferably a hydrocarbon having 16 or more
carbon atoms and 24 or less carbon atoms, the hydrocarbon having a
reactive functional group, which includes, for example,
hexadecenylsuccinic acid, octadecenylsuccinic acid,
eicosenylsuccinic acid, docosenylsuccinic acid, hexadecyl glycidyl
ether, octadecyl glycidyl ether, eicosyl glycidyl ether, docosyl
glycidyl ether, and the like.
The polymer of a hydroxycarboxylic acid having 16 or more carbon
atoms is preferably a polymer of a hydroxycarboxylic acid having 16
or more carbon atoms and 24 and less carbon atoms, which includes,
for example, a polymer of 18-hydroxystearic acid, and the like.
The polymer obtained from a dibasic acid having 2 or more carbon
atoms and 22 or less carbon atoms and a diol having 2 or more
carbon atoms and 22 or less carbon atoms includes, for example, a
polymer obtained from ethylene glycol and sebacic acid, a polymer
obtained from 1,4-butanediol and fumaric acid, a polymer obtained
from 1,6-hexanediol and fumaric acid, a polymer obtained from
1,10-decanediol and sebacic acid, a polymer obtained from
1,12-dodecanediol and 1,12-dodecanedionic acid, and the like.
The polymer of an alkyl (meth)acrylate having 16 or more carbon
atoms is preferably a polymer of an alkyl (meth)acrylate having 16
or more carbon atoms and 24 or less carbon atoms, which includes,
for example, a polymer of hexadecyl methacrylate, a polymer of
octadecyl methacrylate, a polymer of docosyl methacrylate, and the
like.
The polyolefin includes, for example, polyethylene, polypropylene,
polybutylene, polymethylpentene, polytetradecene, polyoctadecene,
polyeicosene, polydocosene, and the like.
The dispersant X preferably has a polyolefin backbone, and more
preferably having a polyethylene backbone and/or a polypropylene
backbone, from the viewpoint of adhesiveness to a film, and the
dispersant X even more preferably has a polypropylene backbone,
from the viewpoint of raising the melting point of the dispersant.
Therefore, among the above dispersible groups, a group derived from
a polyolefin is preferred, a group derived from polyethylene and/or
polypropylene is more preferred, and a group derived from
polypropylene is even more preferred.
The dispersant X is not particularly limited, and obtained by, for
example, reacting raw materials for a basic nitrogen-containing
group and raw materials for a dispersible group.
The raw materials for a basic nitrogen-containing group include
polyalkyleneimines such as polyethyleneimines, polyallylamines,
polyaminoalkyl methacrylates such as poly(dimethylaminoethyl)
methacrylates, and the like.
The number-average molecular weight of the raw materials for the
basic nitrogen-containing group is preferably 100 or more, more
preferably 500 or more, and even more preferably 1,000 or more,
from the viewpoint of adsorbability to an acidic group owned by a
resin, and the number-average molecular weight is preferably 15,000
or less, more preferably 10,000 or less, and even more preferably
5,000 or less, from the viewpoint of dispersibility of the toner
particles and localization to the interface of the film and the
toner particles.
The raw materials for a dispersible group include a halogenated
hydrocarbon having 16 or more carbon atoms, a hydrocarbon having 16
or more carbon atoms having a reactive functional group, a polymer
of a hydroxycarboxylic acid having 16 or more carbon atoms, a
polymer obtained from a dibasic acid having 2 or more carbon atoms
and 22 or less carbon atoms and a diol having 2 or more carbon
atoms and 22 or less carbon atoms, a polymer of an alkyl
(meth)acrylate having 16 or more carbon atoms having a reactive
functional group, a polyolefin having a reactive functional group,
and the like. Among them, the halogenated hydrocarbon having 16 or
more carbon atoms, the hydrocarbon having 16 or more carbon atoms
having a reactive functional group, the polymer of an alkyl
(meth)acrylate having 16 or more carbon atoms and 24 or less carbon
atoms having a reactive functional group, or a polyolefin having a
reactive functional group is preferred, from the viewpoint of
availability and reactivities of the raw materials. The reactive
functional group includes a carboxy group, an epoxy group, a formyl
group, an isocyanate group, and the like, among which a carboxy
group or an epoxy group is preferred, from the viewpoint of safety
and reactivity. Therefore, it is preferable that the compound
having a reactive functional group is a carboxylic acid-based
compound. The carboxylic acid-based compound includes fumaric acid,
maleic acid, ethanoic acid, propanoic acid, butanoic acid, succinic
acid, oxalic acid, malonic acid, tartaric acid, anhydrides thereof,
or alkyl esters thereof of which alkyl has 1 or more carbon atoms
and 3 or less carbon atoms, and the like.
Specific examples of the raw materials for a dispersible group
include halogenated alkanes such as chlorooctadecane,
epoxy-modified polyoctadecyl methacrylate, polyethylene succinic
anhydride, chlorinated polypropylene, polypropylene succinic
anhydride, and the like.
The content of the compound having a polypropylene backbone in the
raw materials for a dispersible group is preferably 70% by mass or
more, more preferably 80% by mass or more, even more preferably 90%
by mass or more, and even more preferably 100% by mass, from the
viewpoint of adhesiveness to a film.
The melting point of the compound having a polypropylene backbone
is preferably 60.degree. C. or higher, more preferably 70.degree.
C. or higher, and even more preferably 80.degree. C. or higher,
from the viewpoint of elevating a melting point of the dispersant,
and the melting point is preferably 160.degree. C. or lower, more
preferably 150.degree. C. or lower, and even more preferably
140.degree. C. or lower, from the viewpoint of adhesiveness to a
film.
The raw materials for a dispersible group having a polypropylene
backbone include, for example, UMEX 100TS, UMEX 110TS, UMEX 1001,
and UMEX 1010, manufactured by Sanyo Chemical Industries, Ltd.;
HARDLEN 13-LP, HARDLEN 13-LLP, HARDLEN 14-LWP, HARDLEN 15-LP,
HARDLEN 15-LLP, HARDLEN 16-LP, HARDLEN DX-526P, HARDLEN CY-9122P,
HARDLEN CY-9124P, HARDLEN HM-21P, HARDLEN M-28P, HARDLEN F-2P,
HARDLEN F-6P, TOYO-TAC M-100, TOYO-TAC M-300, TOYO-TAC M-312,
TOYO-TAC PMA H1000P, and TOYO-TAC PMA-F2, manufactured by TOYOBO
CO., LTD.; SUPERCHLON C, SUPERCHLON L-206, SUPERCHLON 813A,
SUPERCHLON 803M, SUPERCHLON 803MW, SUPERCHLON 803LT, SUPERCHLON
1026, SUPERCHLON 803L, SUPERCHLON 814H, SUPERCHLON 390S, SUPERCHLON
814B, SUPERCHLON 360T, SUPERCHLON 370M, SUPERCHLON 2027MB,
SUPERCHLON 822, SUPERCHLON 892L, SUPERCHLON 930, SUPERCHLON 842LM,
and SUPERCHLON 851L, manufactured by NIPPON PAPER INDUSTRIES CO.,
LTD.; X-10065, X-10088, X-10082, X-10087, X-10053, and X-10052,
manufactured by Baker Hughes, and the like.
The melting point of the dispersant X is 34.degree. C. or higher,
preferably 50.degree. C. or higher, more preferably 65.degree. C.
or higher, and even more preferably 80.degree. C. or higher, from
the viewpoint of adhesiveness to a film, and the melting point is
preferably 150.degree. C. or lower, more preferably 140.degree. C.
or lower, and even more preferably 130.degree. C. or lower, from
the viewpoint of dispersibility of the toner particles.
The content of the dispersant X is preferably 80% by mass or more,
more preferably 90% by mass or more, even more preferably 95% by
mass or more, and even more preferably 100% by mass, of the
dispersant.
The dispersant other than the dispersant X includes copolymers of
alkyl methacrylate/amino group-containing methacrylate, copolymers
of .alpha.-olefin/vinyl pyrrolidone (Antaron V-216), and the
like.
The content of the dispersant X, based on 100 parts by mass of a
total amount of the resin binder and the colorant, is preferably
0.1 parts by mass or more, more preferably 1 part by mass or more,
and even more preferably 2 parts by mass or more, from the
viewpoint of dispersibility of the toner particles and adhesiveness
to a film, and the content is preferably 20 parts by mass or less,
more preferably 15 parts by mass or less, and even more preferably
10 parts by mass or less, from the viewpoint of chargeability of
the toner particles.
[Insulating Liquid]
The insulating liquid in the present invention means a liquid
through which electricity is less likely to flow, and in the
present invention, the conductivity of the insulating liquid is
preferably 1.0.times.10.sup.-11 S/m or less, and more preferably
5.0.times.10.sup.12 S/m or less, and preferably
1.0.times.10.sup.-13 S/m or more.
It is preferable that the insulating liquid in the liquid developer
of the present invention is an insulating liquid containing a
polyisobutene, from the viewpoint of dispersion stability and
chargeability.
The polyisobutene in the present invention refers to a compound
obtained by polymerizing isobutene in accordance with a known
method, for example, a cationic polymerization method using a
catalyst, and thereafter hydrogenating the polymer at a terminal
double bond.
The catalyst usable in the cationic polymerization method includes,
for example, aluminum chloride, an acidic ion-exchanging resin,
sulfuric acid, boron fluoride, and complexes thereof, and the like.
In addition, the polymerization reaction can be controlled by
adding a base to the above catalyst.
The degree of polymerization of the polyisobutene is preferably 8
or less, more preferably 6 or less, even more preferably 5 or less,
even more preferably 4 or less, and even more preferably 3 or less,
from the viewpoint of improving low-temperature fusing ability of
the toner, and the degree of polymerization is preferably 2 or
more, and more preferably 3 or more, from the viewpoint of
controlling corona charger contamination.
It is preferable that an unreacted component of isobutene caused
during the polymerization reaction or a high-boiling point
component having a high degree of polymerization is removed by
distillation. The method of distillation includes, for example, a
simple distillation method, a continuous distillation method, a
steam distillation method, and the like, and these methods can be
used alone or in a combination. The apparatuses used in
distillation are not particularly limited to in materials, shapes,
models, and the like, which include, for example, a distillation
tower packed with a filler material such as Raschig ring, shelved
distillation towers comprising dish-shaped shelves, and the like.
In addition, the theoretical number of shelves showing separating
ability of the distillation tower is preferably 10 shelves or more.
Besides, as to conditions such as feeding rates to the distillation
tower, refluxing ratios, and uptake amounts, the conditions can be
appropriately selected depending upon the distillation
apparatuses.
Since a formed product obtained by the polymerization reaction has
a double bond at a polymerization terminal, a hydrogenated compound
is obtained by a hydrogenation reaction. The hydrogenation reaction
can be carried out by, for example, contacting with hydrogen under
a pressure of from 2 to 10 MPa at a temperature of from 180.degree.
to 230.degree. C. using a hydrogenation catalyst such as nickel or
palladium.
The boiling point of the polyisobutene is preferably 120.degree. C.
or higher, more preferably 140.degree. C. or higher, and even more
preferably 160.degree. C. or higher, from the viewpoint of even
more improving dispersion stability of the toner particles, thereby
improving storage stability, and the boiling point is preferably
300.degree. C. or lower, more preferably 280.degree. C. or lower,
and even more preferably 260.degree. C. or lower, from the
viewpoint of even more improving low-temperature fusing ability of
the liquid developer, and from the viewpoint of even more improving
pulverizability of the toner during wet-milling, thereby providing
a liquid developer having a smaller particle size.
The content of the polyisobutene is preferably 5% by mass or more,
more preferably 20% by mass or more, even more preferably 40% by
mass or more, even more preferably 60% by mass or more, and even
more preferably 80% by mass or more, of the insulating liquid, from
the viewpoint of controlling corona charger contamination.
Commercially available products of the insulating liquid containing
a polyisobutene include "NAS-3," "NAS-4," "NAS-5H," hereinabove
manufactured by NOF Corporation, and the like. Among them, the
commercially available products can be used alone or in a
combination of two or more kinds.
Specific examples of the insulating liquid other than the
polyisobutene include, for example, aliphatic hydrocarbons,
alicyclic hydrocarbons, aromatic hydrocarbons, halogenated
hydrocarbons, polysiloxanes, vegetable oils, and the like. Among
them, the aliphatic hydrocarbons such as liquid paraffin and
isoparaffin are preferred, from the viewpoint of lowering the
viscosity of the liquid developer, and from the viewpoint of odor,
harmlessness, and costs.
Commercially available products of the aliphatic hydrocarbon
include Isopar L and Isopar M, manufactured by Exxon Mobile
Corporation; Lytol, manufactured by Sonneborn; Cactus N12D and
Cactus N14, manufactured by JX Nippon Oil & Energy Corporation,
and the like.
The boiling point of the insulating liquid is preferably
120.degree. C. or higher, more preferably 140.degree. C. or higher,
and even more preferably 160.degree. C. or higher, from the
viewpoint of even more improving dispersion stability of the toner
particles, thereby improving storage stability, and the boiling
point is preferably 300.degree. C. or lower, more preferably
280.degree. C. or lower, and even more preferably 260.degree. C. or
lower, from the viewpoint of even more improving low-temperature
fusing ability of the toner, and from the viewpoint of even more
improving pulverizability of the toner during wet-milling, thereby
providing toner particles having smaller particle sizes. When the
insulating liquids are used in combination of two or more kinds, it
is preferable that a boiling point of a combined insulating liquid
mixture is within the above range.
The viscosity of the insulating liquid at 25.degree. C. is
preferably 1 mPas or more, from the viewpoint of improving
developing ability and from the viewpoint of improving storage
stability of the toner particles in the liquid developer, and the
viscosity is preferably 100 mPas or less, more preferably 50 mPas
or less, even more preferably 20 mPas or less, even more preferably
10 mPas or less, and even more preferably 5 mPas or less.
The liquid developer may properly contain, in addition to the resin
binder, the colorant, the dispersant, and the insulating liquid, an
additive such as a releasing agent, a charge control agent, a
charge control resin, a magnetic particulate, a fluidity improver,
an electric conductivity modifier, a reinforcing filler such as a
fibrous material, an antioxidant, or a cleanability improver.
The liquid developer of the present invention is obtained by mixing
toner particles containing a resin binder and a colorant, a
dispersant, and an insulating liquid, or mixing toner particles
containing a resin binder, a colorant, and a dispersant, and an
insulating liquid.
The methods for producing toner particles include:
a method including melt-kneading toner raw materials containing a
resin binder and a colorant, and pulverizing, preferably
wet-milling, a melt-kneaded product obtained (a production method
A);
a method including powdering raw materials containing a resin
binder in an aqueous medium (a production method B);
a method including stirring an aqueous resin binder dispersion and
a colorant at a high speed (production method C), and the like.
In the present invention, the production method A is preferred,
from the viewpoint of availability of the usable materials, and the
production method B is preferred, from the viewpoint of giving a
function to a resin having an acidic group.
(Production Method A)
First, it is preferable that the toner raw materials containing a
resin binder, a colorant, optionally used additives and the like
are previously mixed with a mixer such as a Henschel mixer, a Super
mixer or a ball-mill, and the mixture is then fed to a kneader, and
the Henschel mixer is more preferred, from the viewpoint of
improving colorant dispersibility in the resin binder. Here, the
dispersant may be mixed and used together with the toner raw
materials such as a resin binder.
The mixing with a Henschel mixer is carried out while adjusting a
peripheral speed of agitation, and agitation time. The peripheral
speed is preferably 10 msec or more and 30 msec or less, from the
viewpoint of improving colorant dispersibility. In addition, the
agitation time is preferably 1 minute or more and 10 minutes or
less, from the viewpoint of improving colorant dispersibility.
Next, the melt-kneading of toner raw materials can be carried out
with a known kneader, such as a tightly closed kneader, a
single-screw or twin-screw kneader, or a continuous open-roller
type kneader. In the method for production of the present
invention, an open-roller type kneader is preferred, from the
viewpoint of improving colorant dispersibility, and from the
viewpoint of improving an yield of the toner particles after
pulverization.
The open-roller type kneader refers to a kneader of which
melt-kneading unit is an open type, not being tightly closed, which
can easily dissipate the kneading heat generated during the
melt-kneading. The open-roller type kneader used in the present
invention is provided with a plurality of feeding ports for raw
materials and a discharging port for a kneaded mixture along the
shaft direction of the roller, and it is preferable that the
open-roller type kneader is a continuous open-roller type kneader,
from the viewpoint of production efficiency.
It is preferable that the open-roller type kneader comprises at
least two kneading rollers having different temperatures.
It is preferable that the setting temperatures of the rollers are
such that the set temperature is equal to or lower than a
temperature that is 10.degree. C. higher than the softening point
of the resin, from the viewpoint of improving miscibility of the
toner raw materials.
In addition, it is preferable that the set temperature of the
roller at an upstream side is higher than the set temperature of
the roller at a downstream side, from the viewpoint of making the
adhesiveness of the kneaded product to the roller at an upstream
side favorable and strongly kneading at a downstream side.
It is preferable that the rollers have peripheral speeds that are
different from each other. In the open roller-type kneader provided
with the above two rollers, it is preferable that the heat roller
having a higher temperature is a high-rotation roller, and that the
cooling roller having a lower temperature is a low-rotation roller,
from the viewpoint of improving fusing ability of the liquid
developer.
The peripheral speed of the high-rotation roller is preferably 2
m/min or more, and more preferably 5 m/min or more, and preferably
100 m/min or less, and more preferably 75 m/min or less. The
peripheral speed of the low-rotation roller is preferably 2 m/min
or more, and more preferably 4 m/min or more, and preferably 100
m/min or less, more preferably 60 m/min or less, and even more
preferably 50 m/min or less. Also, the ratio of the peripheral
speeds of the two rollers, i.e. low-rotation roller/high-rotation
roller, is preferably 1/10 or more, and more preferably 3/10 or
more, and preferably 9/10 or less, and more preferably 8/10 or
less.
In addition, structures, size, materials and the like of each of
the rollers are not particularly limited. The surface of the roller
comprises a groove used in kneading, and the shapes of grooves
include linear, spiral, wavy, rugged or other forms.
Next, the melt-kneaded product is cooled to an extent that is
pulverizable, and the cooled product is subjected to a pulverizing
step and optionally a classifying step, whereby the toner particles
can be obtained.
The pulverizing step may be carried out in divided multi-stages.
For example, the melt-kneaded product may be roughly pulverized to
a size of from 1 to 5 mm or so, and the roughly pulverized product
may then be further finely pulverized. In addition, in order to
improve productivity during the pulverizing step, the melt-kneaded
product may be mixed with fine inorganic particles made of
hydrophobic silica or the like, and then pulverized.
The pulverizer suitably used in the rough pulverization includes,
for example, an atomizer, Rotoplex, and the like, or a hammer-mill
or the like may be used. In addition, the pulverizer suitably used
in the fine pulverization includes a fluidised bed opposed jet
mill, an air jet mill, a mechanical mill, and the like.
The classifier usable in the classification step includes an air
classifier, a rotor type classifier, a sieve classifier, and the
like. Here, the pulverizing step and the classifying step may be
repeated as occasion demands.
The toner particles obtained in the production method A have a
volume-median particle size D.sub.50 of preferably 3 .mu.m or more,
and more preferably 4 .mu.m or more, and preferably 15 .mu.m or
less, and more preferably 12 .mu.m or less, from the viewpoint of
improving productivity of the wet-milling step described later.
Here, the volume-median particle size D.sub.50 means a particle
size of which cumulative volume frequency calculated on a volume
percentage is 50% counted from the smaller particle sizes. Here, it
is preferable that the toner particles are mixed with a dispersant
and an insulating liquid, and then further finely pulverized with
wet-milling or the like.
(Production Method B)
The production method B includes, for example: (B1) a method
including previously forming primary particles containing a resin
binder in an aqueous medium, and thereafter aggregating and
unifying the primary particles; (B2) a method including previously
forming primary particles containing a resin binder in an aqueous
medium, and thereafter fusing the primary particles; and (B3) a
method including dispersing raw materials containing a resin binder
in an aqueous medium, and powdering the dispersion, and the
like.
In the present invention, the method (B1) is preferred, and a
method including (1) introducing an aqueous medium to a mixed
solution or dispersion prepared by dissolving or dispersing raw
materials containing a resin binder in an organic solvent, and
thereafter removing the organic solvent, to provide an aqueous
dispersion of primary particles containing a resin binder; and (2)
aggregating and unifying the primary particles is preferred.
Specific examples of the method (B2) include a method including
subjecting a radical-polymerizable monomer solution in which a
resin binder is dissolved to an emulsion polymerization to provide
fine resin particles, and fusing the fine resin particles obtained
in an aqueous medium (see, Japanese Patent Laid-Open No.
2001-42568), and specific examples of the method (B3) include a
method including heating and melting raw materials containing a
resin binder, dispersing the molten raw materials in an aqueous
medium without containing an organic solvent, while maintaining the
molten state of the resin binder, and subsequently drying the
dispersion (see, Japanese Patent Laid-Open No. 2001-235904), and
the like, respectively.
The step (1) is a step of introducing an aqueous medium to a mixed
solution or dispersion prepared by dissolving or dispersing raw
materials containing a resin binder in an organic solvent, and
thereafter removing the organic solvent, to provide an aqueous
dispersion of primary particles containing a resin binder.
The amount of the organic solvent used is preferably 100 parts by
mass or more and 1,000 parts by mass or less, based on 100 parts by
mass of the resin binder. Water and optionally a neutralizing agent
is mixed with stirring with a mixed solution, and the organic
solvent is removed from the dispersion obtained, whereby an aqueous
dispersion of primary particles of a self-dispersible resin can be
obtained. The organic solvent includes those mentioned above.
The amount of the aqueous solvent used is preferably 100 parts by
mass or more and 3,000 parts by mass or less, based on 100 parts by
mass of the organic solvent. Here, the aqueous medium usable in the
method (1) may contain a solvent such as an organic solvent, and
water is contained in an amount of preferably 50% by mass or more,
preferably 70% by mass or more, more preferably 90% by mass or
more, and even more preferably 99% by mass or more.
When a mixture is agitated, a mixing agitator generally used such
as anchor blades can be used. The neutralizing agent includes
alkali metal compounds such as lithium hydroxide, sodium hydroxide,
and potassium hydroxide; organic bases such as ammonia,
trimethylamine, ethylamine, diethylamine, triethylamine,
triethanolamine, and tributylamine. The amount of the neutralizing
agent, based on the acid value of the polyester after the reaction
used in neutralization, is preferably 0.5 equivalents or more, more
preferably 0.7 equivalents or more, and even more preferably 0.8
equivalents or more, and 1.5 equivalents or less, more preferably
1.3 equivalents or less, and even more preferably 1.2 equivalents
or less.
For the intended purposes of lowering the melt viscosity and the
melting point of the resin binder, and improving dispersibility of
produced primary particles, a dispersant can be used. The
dispersant includes, for example, water-soluble polymers such as
polyvinyl alcohols, methyl cellulose, ethyl cellulose, hydroxyethyl
cellulose, carboxymethyl cellulose, sodium polyacrylate, and sodium
polymethacrylate; anionic surfactants such as sodium
dodecylbenzenesulfonate, sodium octadecylsulfate, sodium oleate,
sodium laurate, and potassium stearate; cationic surfactants such
as laurylamine acetate, stearylamine acetate, and
lauryltrimethylammonium chloride; amphoteric surfactants such as
lauryldimethylamine oxide; and inorganic salts such as calcium
phosphate, aluminum hydroxide, calcium sulfate, and calcium
carbonate. The amount of the dispersant used, based on 100 parts by
mass of the resin binder, is preferably 20 parts by mass or less,
more preferably 15 parts by mass or less, and even more preferably
10 parts by mass or less, from the viewpoint of emulsion stability
and detergency.
The solid content concentration of the primary particles containing
a resin binder obtained by the step (1) (hereinafter also simply
referred to as primary particles) is preferably 7% by mass or more,
and preferably 50% by mass or less, and more preferably 40% by mass
or less, of the dispersion, from the viewpoint of stability of the
dispersion and handling of the dispersion in the aggregating step.
Here, the solid content includes a non-volatile component such as
resins.
The average particle size of the primary particles is preferably
0.05 .mu.m or more, and preferably 3 .mu.m or less, more preferably
1 .mu.m or less, and even more preferably 0.8 .mu.m or less, from
the viewpoint of uniformly aggregating the primary particles in the
subsequent step. In the present invention, the average particle
size of the primary particles refers to a volume-median particle
size D.sub.50, and can be measured with a laser diffraction
particle size analyzer or the like.
Subsequently, the step of aggregating and unifying the primary
particles obtained in the step (1) (step (2)) will be
explained.
In the step (2), the solid content concentration in the system in
the aggregating step of aggregating the primary particles obtained
in the step (1) can be adjusted by adding water to the dispersion
of a resin binder, and the solid content concentration is
preferably 5% by mass or more, and preferably 50% by mass or less,
more preferably 30% by mass or less, and even more preferably 20%
by mass or less, in order to cause uniform aggregation.
The pH inside the system in the aggregating step is preferably 2 or
more, and preferably 10 or less, and more preferably 9 or less,
from the viewpoint of satisfying dispersion stability of the liquid
mixture and aggregating ability of fine particles of a resin binder
and the like.
It is preferable that the temperature inside the system in the
aggregating step is a temperature of equal to or higher than a
temperature calculated as a softening point of the resin binder
minus 80.degree. C. and a temperature equal to or lower than the
softening point, from the same viewpoint.
In addition, the additive such as a colorant may be previously
mixed with a resin binder when the primary particles are prepared,
or a dispersion is prepared by separately dispersing each of
additives in a dispersion medium such as water, each of the
dispersions is mixed with the primary particles to be subjected to
an aggregating step. When an additive is previously mixed with a
resin binder when the primary particles are prepared, it is
preferable that a resin binder and an additive are previously
melt-kneaded.
In the aggregating step, an aggregating agent can be added in order
to effectively carry out the aggregation. As the aggregating agent,
a cationic surfactant of a quaternary salt, a polyethylencimine or
the like in an organic system, or an inorganic ammonium salt, an
inorganic metal salt, a divalent or higher polyvalent metal complex
or the like in an inorganic system is used. The inorganic ammonium
salt includes ammonium sulfate, ammonium chloride, and the like.
The inorganic metal salt includes metal salts such as sodium
sulfate, sodium chloride, calcium chloride, calcium nitrate, barium
chloride, magnesium chloride, zinc chloride, aluminum chloride and
aluminum sulfate; polymers of inorganic metal salts such as
poly(aluminum chloride), poly(aluminum hydroxide), and poly(calcium
sulfide), and the like.
The amount of the aggregating agent used, is preferably 50 parts by
mass or less, and more preferably 40 parts by mass or less, based
on 100 parts by mass of the resin binder, from the viewpoint of
environmental resistance property of the toner.
Subsequently, the aggregated particles containing at least a resin
binder obtained in the above aggregating step are heated and
unified (unifying step).
The temperature inside the system in the unifying step is
preferably from a temperature equal to or higher than a temperature
calculated as a softening point of the resin binder minus
50.degree. C. to a temperature equal to or lower than a temperature
calculated as a softening point plus 10.degree. C., more preferably
from a temperature equal to or higher than a temperature calculated
as a softening point minus 45.degree. C. to a temperature equal to
or lower than a temperature calculated as a softening point plus
10.degree. C., and even more preferably from a temperature equal to
or higher than a temperature calculated as a softening point minus
40.degree. C. to a temperature equal to or lower than a temperature
calculated as a softening point plus 10.degree. C., from the
viewpoint of particle sizes, the particle size distribution, the
shape control, and fusibility of the particles of the toner. In
addition, it is preferable that the agitation rate is a rate at
which the aggregated particles do not precipitate. Here, in the
present invention, when two or more kinds of resins are used as
resin binders, a softening point of a mixed resin is defined as a
softening point of the resin binder.
In the aggregating step, a nonionic surfactant may be used, from
the viewpoint of improving productivity, and an anionic surfactant
may be used, from the viewpoint of dispersibility of the toner,
respectively.
The unified particles obtained by the step (2) are appropriately
subjected to a liquid-solid separation step such as filtration, a
washing step, and a drying step, whereby toner particles can be
obtained.
In addition, in the drying step, any methods such as vibrating
fluidized bed drying method, spray-drying method, freeze-drying
method, or flush-jet method can be employed.
The volume-median particle size D.sub.50 of the toner particles
obtained in the production method B is preferably 0.5 .mu.m or
more, more preferably 1.0 .mu.m or more, and even more preferably
1.5 .mu.m or more, from the viewpoint of lowering the viscosity of
the liquid developer, and the volume-median particle size is
preferably 5 .mu.m or less, more preferably 3 .mu.m or less, and
even more preferably 2.5 .mu.m or less, from the viewpoint of
improving image quality of the liquid developer.
The content of the toner particles, based on 100 parts by mass of
the insulating liquid, is preferably 10 parts by mass or more, more
preferably 20 parts by mass or more, even more preferably 30 parts
by mass or more, even more preferably 40 parts by mass or more, and
even more preferably 50 parts by mass or more, from the viewpoint
of high-speed printability, and the content is preferably 100 parts
by mass or less, more preferably 80 parts by mass or less, even
more preferably 70 parts by mass or less, and even more preferably
60 parts by mass or less, from the viewpoint of improving
dispersion stability.
As the method for mixing toner particles, a dispersant, and an
insulating liquid, or mixing toner particles and an insulating
liquid, a method including stirring the components with an
agitation mixer or the like is preferred.
The agitation mixer is, but not particularly limited to, preferably
high-speed agitation mixers, from the viewpoint of improving
productivity and storage stability of the dispersion of toner
particles. Specific examples are preferably DESPA, manufactured by
ASADA IRON WORKS CO., LTD.; T.K. HOMOGENIZING MIXER, T.K.
HOMOGENIZING DISPER, T.K. ROBOMIX, hereinabove manufactured by
PRIMIX Corporation; CLEARMIX, manufactured by M Technique Co.,
Ltd.; KADY Mill, manufactured by KADY International, and the
like.
The toner particles are previously dispersed by mixing components
with a high-speed agitation mixer, whereby a dispersion of toner
particles can be obtained, which in turn improves productivity of a
liquid developer by the subsequent wet-milling.
The solid content concentration of the liquid developer is
preferably 10% by mass or more, more preferably 15% by mass or
more, and even more preferably 20% by mass or more, from the
viewpoint of improving optical density, and the solid content
concentration is preferably 50% by mass or less, more preferably
45% by mass or less, and even more preferably 40% by mass or less,
from the viewpoint of improving dispersion stability of the toner
particles, thereby improving storage stability.
As always provided, it is preferable that the liquid developer is
obtained by dispersing toner particles obtained in the production
method A in an insulating liquid, and thereafter wet-milling a
dispersion, from the viewpoint of making particle sizes of the
toner particles in the liquid developer smaller, and from the
viewpoint of lowering the viscosity of the liquid developer.
Further, when wet-milling is carried out, the solid content
concentration of the dispersion of the toner particles obtained by
mixing toner particles, a dispersant, and an insulating liquid is
preferably 20% by mass or more, more preferably 30% by mass or
more, and even more preferably 33% by mass or more, from the
viewpoint of improving optical density, and the solid content
concentration is preferably 50% by mass or less, more preferably
45% by mass or less, and even more preferably 40% by mass or less,
from the viewpoint of improving dispersion stability of the toner
particles, thereby improving storage stability.
The wet-milling refers to a method of subjecting toner particles
dispersed in an insulating liquid to a mechanical milling treatment
in the state of dispersion in the insulating liquid.
As the apparatus used, for example, generally used agitation mixers
such as anchor blades can be used. Among the agitation mixers, the
apparatuses include high-speed agitation mixers such as DESPA,
manufactured by ASADA IRON WORKS CO., LTD., and T.K. HOMOGENIZING
MIXER, manufactured by PRIMIX Corporation; pulverizers or kneaders,
such as roller mills, beads-mills, kneaders, and extruders; and the
like. These apparatuses can be used in a combination of plural
apparatuses.
Among these apparatuses, use of beads-mill is preferred, from the
viewpoint of making particle sizes of toner particles smaller, from
the viewpoint of improving dispersion stability of the toner
particles, thereby improving storage stability, and from the
viewpoint of lowering the viscosity of the dispersion.
By controlling particle sizes and filling ratios of media used,
peripheral speeds of rotors, residence time, or the like in the
beads-mill, toner particles having a desired particle size and a
particle size distribution can be obtained.
As described above, in a case where a liquid developer is obtained
by producing toner particles according to the production method A,
and further wet-milling the toner particles, it is preferable that
the liquid developer of the present invention is produced by a
method including: step 1: melt-kneading a resin binder containing a
polyester-based resin and a colorant, and pulverizing a kneaded
product obtained, to provide toner particles; step 2: adding a
dispersant to the toner particles obtained in the step 1, and
dispersing the toner particles in an insulating liquid to provide a
dispersion of toner particles; and step 3: subjecting the
dispersion of toner particles obtained in the step 2 to
wet-milling, to provide a liquid developer.
The solid content concentration of the liquid developer obtained by
wet-milling is preferably 10% by mass or more, more preferably 15%
by mass or more, and even more preferably 20% by mass or more, from
the viewpoint of improving optical density, and the solid content
concentration is preferably 50% by mass or less, more preferably
45% by mass or less, and even more preferably 40% by mass or less,
from the viewpoint of improving dispersion stability of the toner
particles, thereby improving storage stability.
The volume-median particle size D.sub.50 of the toner particles in
the liquid developer is preferably 0.5 .mu.m or more, more
preferably 1.0 .mu.m or more, and even more preferably 1.5 .mu.m or
more, from the viewpoint of lowering the viscosity of the liquid
developer, and the volume-median particle size is preferably 5
.mu.m or less, more preferably 3 .mu.m or less, and even more
preferably 2.5 .mu.m or less, from the viewpoint of improving image
quality of the liquid developer.
The viscosity of the liquid developer, the solid content
concentration of which is 25% by mass, at 25.degree. C. is
preferably 1 mPas or more, more preferably 2 mPas or more, and even
more preferably 3 mPas or more, from the viewpoint of
developability, and the viscosity is preferably 50 mPas or less,
more preferably 40 mPas or less, and even more preferably 30 mPas
or less, from the viewpoint of high-speed printing.
By using the liquid developer of the present invention, a fused
image can be printed on a resin film. As the resin film, a
polyethylene terephthalate film can be used. In addition, in a case
where of a liquid developer containing a dispersant X of which
dispersible group has a polypropylene backbone, excellent fusing
ability is exhibited even with a polypropylene film. Also, in a
case where a resin having an acidic group is a modified polyester
having a urethane bond, excellent fusing ability is exhibited even
with a nylon film.
Specific methods for printing a fused image on a resin film using a
liquid developer include, for example, a method including charging
step of charging a photoconductor; an exposing step of exposing a
photoconductor; a developing step of adhering toner particles in a
liquid developer to an electrostatic latent image formed on the
photoconductor to form a toner image; a transferring step of
transferring the formed toner image to a resin film; and a fusing
step of heating a transferred toner image to evaporate and remove
an insulating liquid contained in the toner image, and at the same
time fusing the toner image on the resin film.
Here, the liquid developer of the present invention can be
favorably fused also to an untreated resin film. Therefore, since
the pretreatment (application of surface-modifying agent) of the
resin film which has been conventionally carried out is not
necessitated upon image printing to a resin film, large-scaled
printing apparatus and complications of the system can be avoided
by using the liquid developer of the present invention. In
addition, high-image quality formation of the fused images can be
accomplished.
With regard to the embodiments described above, the present
invention further discloses the following liquid developers and
methods for producing a liquid developer.
<1> A liquid developer containing a resin binder, a colorant,
a dispersant, and an insulating liquid, wherein the resin binder
contains a resin having an acidic group, and wherein the dispersant
contains a dispersant X having at least one basic
nitrogen-containing group selected from the group consisting of an
amino group, an imino group, a cyano group, an azo group, a diazo
group, and an azide group, and wherein a melting point of the
dispersant X is 34.degree. C. or higher.
<2> The liquid developer according to the above <1>,
wherein the resin having an acidic group is a polyester-based
resin. <3> The liquid developer according to the above
<2>, wherein the polyester-based resin is a polyester resin
or a composite resin containing a polyester resin and a styrenic
resin. <4> The liquid developer according to the above
<3>, wherein the polyester resin is a polycondensate of an
alcohol component containing a dihydric or higher polyhydric
alcohol and a carboxylic acid component containing a dicarboxylic
or higher polycarboxylic acid compound. <5> The liquid
developer according to the above <4>, wherein the dihydric or
higher polyhydric alcohol contains an aliphatic diol having 2 or
more carbon atoms and 20 or less carbon atoms, and preferably 2 or
more carbon atoms and 15 or less carbon atoms and/or an alkylene
oxide adduct of bisphenol A represented by the formula (I).
<6> The liquid developer according to any one of the above
<1> to <5>, wherein the melting point of the dispersant
X is 34.degree. C. or higher, preferably 50.degree. C. or higher,
more preferably 65.degree. C. or higher, and even more preferably
80.degree. C. or higher, and 150.degree. C. or lower, preferably
140.degree. C. or lower, and more preferably 130.degree. C. or
lower. <7> The liquid developer according to any one of the
above <1> to <6>, wherein the basic nitrogen-containing
group in the dispersant X is an imino group and/or an amino group.
<8> The liquid developer according to any one of the above
<1> to <7>, wherein the dispersant X is obtained by
reacting raw materials for a basic nitrogen-containing group and
raw materials for a dispersible group. <9> The liquid
developer according to the above <8>, wherein the
number-average molecular weight of the raw materials for the basic
nitrogen-containing group is 100 or more, preferably 500 or more,
and more preferably 1,000 or more, and 15,000 or less, preferably
10,000 or less, and even more preferably 5,000 or less. <10>
The liquid developer according to any one of the above <1> to
<9>, wherein the dispersant X contains a group derived from
at least one member selected from the group consisting of
hydrocarbons having 16 or more carbon atoms, hydrocarbons having 16
or more carbon atoms partly substituted with a halogen atom,
hydrocarbons having 16 or more carbon atoms having a reactive
functional group, a polymer of a hydroxycarboxylic acid having 16
or more carbon atoms, a polymer obtained from a dibasic acid having
2 or more carbon atoms and 22 or less carbon atoms and a diol
having 2 or more carbon atoms and 22 or less carbon atoms, a
polymer of an alkyl (meth)acrylate having 16 or more carbon atoms,
and a polyolefin. <11> The liquid developer according to any
one of the above <1> to <10>, wherein the boiling point
of the insulating liquid is 120.degree. C. or higher, preferably
140.degree. C. or higher, and more preferably 160.degree. C. or
higher, and 300.degree. C. or lower, preferably 280.degree. C. or
lower, and more preferably 260.degree. C. or lower. <12> The
liquid developer according to any one of the above <1> to
<11>, wherein the viscosity of the insulating liquid at
25.degree. C. is 1 mPas or more, and 100 mPas or less, preferably
50 mPas or less, more preferably 20 mPas or less, even more
preferably 10 mPas or less, and even more preferably 5 mPas or
less. <13> The liquid developer according to any one of the
above <1> to <12>, wherein the insulating liquid
contains a polyisobutene. <14> The liquid developer according
to the above <13>, wherein the degree of polymerization of
the polyisobutene is 2 or more, and preferably 3 or more, and 8 or
less, preferably 6 or less, more preferably 5 or less, even more
preferably 4 or less, and even more preferably 3 or less.
<15> The liquid developer according to the above <13>
or <14>, wherein the boiling point of the polyisobutene is
120.degree. C. or higher, preferably 140.degree. C. or higher, and
more preferably 160.degree. C. or higher, and 300.degree. C. or
lower, preferably 280.degree. C. or lower, and more preferably
260.degree. C. or lower. <16> The liquid developer according
to any one of the above <1> to <15>, wherein the
dispersant X comprises a polyethylene backbone and/or a
polypropylene backbone. <17> The liquid developer according
to any one of the above <1> to <16>, wherein the resin
having an acidic group is a modified polyester resin having a
urethane bond. <18> A method for printing a fused image on a
resin film using a liquid developer as defined in any one of the
above <1> to <17>, wherein the above resin film is a
polyethylene terephthalate film. <19> A method for printing a
fused image on a resin film using a liquid developer as defined in
the above <16> or <17>, wherein the resin film is a
polypropylene film. <20> A method for printing a fused image
on a resin film using a liquid developer as defined in the above
<17>, wherein the resin film is a nylon film.
The present invention will be described hereinbelow more
specifically by the Examples, without intending to limit the
present invention to these Examples. The physical properties of the
resins and the like were measured in accordance with the following
methods.
[Softening Point of Resin and Toner Particles]
Using a flow tester "CFT-500D," manufactured by Shimadzu
Corporation, a 1 g sample is extruded through a nozzle having a
diameter of 1 mm and a length of 1 mm with applying a load of 1.96
MPa thereto with a plunger, while heating the sample at a heating
rate of 6.degree. C./min. The softening point refers to a
temperature at which half of the sample flows out, when plotting a
downward movement of the plunger of the flow tester against
temperature.
[Glass Transition Temperature of Resin and Toner Particles]
Using a differential scanning calorimeter "Q20," manufactured by TA
Instruments, a 0.01 to 0.02 g sample is weighed out in an aluminum
pan, heated to 200.degree. C., and cooled from that temperature to
0.degree. C. at a cooling rate of 10.degree. C./min. Next, the
temperature of the sample is raised at a heating rate of 10.degree.
C./min to measure endothermic peaks. A temperature of an
intersection of the extension of the baseline of equal to or lower
than the highest temperature of endothermic peak and the tangential
line showing the maximum inclination between the kick-off of the
peak and the top of the peak is defined as a glass transition
temperature.
[Acid Value of Resin]
The acid value is determined by a method according to JIS K0070
except that only the determination solvent is changed from a mixed
solvent of ethanol and ether as prescribed in JIS K0070 to a mixed
solvent of acetone and toluene in a volume ratio of
acetone:toluene=1:1.
[Volume-Median Particle Size D.sub.50 and CV Value of Resin
Particles and Colorant Particles] (1) Measuring Apparatus: Laser
diffraction particle size analyzer "LA-920" manufactured by HORIBA,
Ltd. (2) Measurement Conditions: To the measurement cell is added
distilled water, and a volume-median particle size is measured at a
temperature where the absorbance is within an appropriate
range.
In addition, a CV value (%) is calculated in accordance with the
following formula:
.times..times..times..times..times..times..times..times..times..times..ti-
mes..times..times..times..times..times..times..times..times..times..times.-
.times..times. ##EQU00001##
[Solid Content Concentration of Aqueous Dispersion of Resin]
The water content is measured using an infrared moisture
determination balance "FD-230" manufactured by Kett Electric
Laboratory using a 5 g measurement sample at a drying temperature
of 150.degree. C. with a measurement mode 96 (monitoring time: 2.5
min/fluctuation width: 0.05%). The solid content concentration is
calculated in accordance with the following formula: Solid Content
Concentration (% by Mass)=100-M wherein M is a water content (% by
mass).
[Volume-Median Particle Size of Toner Particles Before Mixing With
Insulating Liquid] Measuring Apparatus: Coulter Multisizer II,
manufactured by Beckman Coulter, Inc. Aperture Diameter: 100 .mu.m
Analyzing Software: Coulter Multisizer AccuComp Ver. 1.19,
manufactured by Beckman Coulter, Inc. Electrolytic Solution:
Isotone II, manufactured by Beckman Coulter, Inc. Dispersion:
EMULGEN 109P, manufactured by Kao Corporation, polyoxyethylene
lauryl ether, HLB (Griffin): 13.6, is dissolved in the above
electrolytic solution to adjust to a concentration of 5% by mass to
provide a dispersion. Dispersion Conditions: Ten milligrams of a
measurement sample is added to 5 mL of the above dispersion, and
the mixture is dispersed for 1 minute with an ultrasonic disperser
(name of machine: US-1, manufactured by SND Co., Ltd., output: 80
W), and 25 mL of the above electrolytic solution is then added to
the dispersion, and further dispersed with the ultrasonic disperser
for 1 minute, to prepare a sample dispersion. Measurement
Conditions: The above sample dispersion is added to 100 mL of the
above electrolytic solution to adjust to a concentration at which
particle sizes of 30,000 particles can be measured in 20 seconds,
and the 30,000 particles are measured, and a volume-median particle
size D.sub.50 is obtained from the particle size distribution.
[Number-Average Molecular Weight of Raw Materials for Basic
Nitrogen-Containing Group]
The number-average molecular weight is obtained by measuring a
molecular weight distribution in accordance with a gel permeation
chromatography (GPC) method as shown hereinbelow. (1) Preparation
of Sample Solution
A polyalkyleneimine is dissolved in a solution prepared by
dissolving Na.sub.2SO.sub.4 in an aqueous 1% acetic acid solution
at 0.15 mol/L so as to have a concentration of 0.2 g/100 mL. Next,
this solution is filtered with a fluororesin filter "FP-200,"
manufactured by Sumitomo Electric Industries, Ltd., having a pore
size of 0.2 .mu.m, to remove insoluble components, to provide a
sample solution. (2) Molecular Weight Measurements
Using the following measurement apparatus and analyzing column, the
measurement is taken by allowing a solution prepared by dissolving
Na.sub.2SO.sub.4 in an aqueous 1% acetic acid solution at 0.15
mol/L to flow through a column as an eluent at a flow rate of 1 mL
per minute, stabilizing the column in a thermostat at 40.degree.
C., and loading 100 .mu.L of a sample solution thereto. The
molecular weight of the sample is calculated based on the
previously drawn calibration curve. At this time, a calibration
curve which is drawn from several kinds of standard pullulans,
manufactured by SHOWA DENKO CORPORATION, P-5 (Mw
5.9.times.10.sup.3), P-50 (Mw 4.73.times.10.sup.4), P-200 (Mw
2.12.times.10.sup.5), and P-800 (Mw 7.08.times.10.sup.5) as
standard samples is used. The values within the parentheses show
molecular weights. Measurement Apparatus: HLC-8320GPC, manufactured
by Tosoh Corporation Analyzing Column; .alpha.+.alpha.-M+.alpha.-M,
manufactured by Tosoh Corporation.
[Melting Points of Raw Materials for Dispersible Group and
Dispersant]
Using a differential scanning calorimeter "Q20," manufactured by TA
Instruments, a 0.01 to 0.02 g sample is weighed out in an aluminum
pan, and cooled from room temperature to -50.degree. C. at a
cooling rate of 10.degree. C./min. Next, the temperature of the
sample is raised from -50.degree. to 200.degree. C. at a heating
rate of 10.degree. C./min to measure endothermic peaks. The top of
the peak of the endothermic peak is defined as a melting point.
[Boiling Point of Insulating Liquid]
Using a differential scanning calorimeter "DSC210," manufactured by
Seiko Instruments Inc., a 6.0 to 8.0 g sample is weighed out in an
aluminum pan, the temperature of the sample is raised to
350.degree. C. at a heating rate of 10.degree. C./min to measure
endothermic peaks. The highest temperature side of the endothermic
peak is defined as a boiling point.
[Conductivity of Insulating Liquid]
A 40 mL glass sample vial "Vial with screw cap, No. 7,"
manufactured by Maruemu Corporation is charged with 25 g of an
insulating liquid. The conductivity is determined by immersing an
electrode in an insulating liquid, taking 20 measurements for
conductivity at 25.degree. C. with a non-aqueous conductivity meter
"DT-700," manufactured by Dispersion Technology, Inc., and
calculating an average thereof. The smaller the numerical figures,
the higher the resistance.
[Viscosities at 25.degree. C. of Insulating Liquid and Liquid
Developer Solid Content Concentration of Which Is 25% by Mass]
A 10-mL glass sample vial with screw cap is charged with 6 to 7 mL
of a measurement solution, and a viscosity at 25.degree. C. is
measured with a torsional oscillation type viscometer "VISCOMATE
VM-10A-L," manufactured by SEKONIC CORPORATION.
[Solid Content Concentrations of Dispersion of Toner Particles and
Liquid Developer Solid Content Concentration of Which Is 25% by
Mass]
Ten parts by mass of a sample is diluted with 90 parts by mass of
hexane, and the dilution is spun with a centrifuge "H-201F,"
manufactured by KOKUSAN Co., Ltd. at a rotational speed of 25,000
r/min for 20 minutes. After allowing the mixture to stand, the
supernatant is removed by decantation, the mixture is then diluted
with 90 parts by mass of hexane, and the dilution is again
centrifuged under the same conditions as above. The supernatant is
removed by decantation, and a lower layer is then dried with a
vacuum dryer at 0.5 kPa and 40.degree. C. for 8 hours. The solid
content concentration is calculated according to the following
formula:
.times..times..times..times. .times..times. .times..times.
.times..times..times..times..times..times..times..times..times..times..ti-
mes..times..times..times..times..times..times..times..times..times..times.-
.times..times..times. ##EQU00002##
[Volume-Median Particle Size D.sub.50 and CV Value of Toner
Particles in Liquid Developer]
A volume-median particle size D.sub.50 is determined with a laser
diffraction/scattering particle size measurement instrument
"Mastersizer 2000," manufactured by Malvern Instruments, Ltd., by
charging a cell for measurement with Isopar L, manufactured by
Exxon Mobile Corporation, isoparaffin, viscosity at 25.degree. C.:
1 mPas, under conditions that a particle refractive index is 1.58,
imaginary part being 0.1, and a dispersion medium refractive index
is 1.42, at a concentration that gives a scattering intensity of
from 5 to 15%.
In addition, a CV value (%) is calculated in accordance with the
following formula:
.times..times..times..times..times..times..times..times..times..times..ti-
mes..times..times..times..times..times..times..times..times..times..times.-
.times..times. ##EQU00003##
Production Example 1 of Resins [Resins A and B]
A 10-L four-neck flask equipped with a nitrogen inlet tube, a
dehydration tube equipped with a fractional distillation tube
through which hot water at 98.degree. C. was allowed to flow, a
stirrer, and a thermocouple was charged with raw material monomers
and an esterification catalyst as listed in Table 1. The contents
were heated to 180.degree. C. and then heated to 210.degree. C.
over 5 hours, and the mixture was reacted until a reaction
percentage reached 90%, the reaction mixture was further reacted at
8.3 kPa, and the reaction was terminated at a point where a
softening point reached an intended value, to provide a polyester
resin having the physical properties as listed in Table 1. Here, in
Production Examples of Resins, the reaction percentage refers to a
value calculated by: [amount of generated water in reaction
(mol)/theoretical amount of generated water (mol)].times.100.
Production Example 2 of Resins [Resins C and D]
A 10-L four-neck flask equipped with a nitrogen inlet tube, a
dehydration tube, a stirrer, and a thermocouple was charged with
raw material monomers, an esterification catalyst, and a
polymerization inhibitor as listed in Table 1. The contents were
reacted at 210.degree. C., and the reaction mixture was reacted
until a reaction percentage reached 90%. Further, the reaction
mixture was reacted at 8.3 kPa, and a reaction was terminated at a
point where a softening point reached an intended value, to provide
a polyester resin having the physical properties as listed in Table
1.
Production Example 3 of Resin [Resin E]
A 10-L four-neck flask equipped with a nitrogen inlet tube, a
dehydration tube, a stirrer, and a thermocouple was charged with
raw material monomers and an esterification catalyst as listed in
Table 1. The contents were reacted at 235.degree. C., and the
reaction mixture was reacted until a reaction percentage reached
90%. Further, the reaction mixture was reacted at 8.3 kPa, and a
reaction was terminated at a point where a softening point reached
an intended value, to provide a polyester resin having the physical
properties as listed in Table 1.
Production Example 4 of Resin [Resin F]
A 10-L four-neck flask equipped with a nitrogen inlet tube, a
dehydration tube, a stirrer, and a thermocouple was charged with
raw material monomers for a polyester resin other than fumaric acid
and trimellitic anhydride and an esterification catalyst as listed
in Table 1. The contents were heated with a mantle heater to
230.degree. C., and then reacted at 230.degree. C. for 8 hours, and
further reduced pressure to 8.3 kPa and reacted for one hour. The
temperature of the reaction mixture was lowered to 170.degree. C.,
and raw material monomers for a styrenic resin, a dually reactive
monomer, and a polymerization initiator as listed in Table 1 were
added dropwise from a dropping funnel over one hour. While holding
the temperature at 170.degree. C., the addition polymerization
reaction was aged for one hour. Thereafter, the reaction mixture
was heated to 210.degree. C., and subjected to removal of the raw
material monomers for the styrenic resin at 8.3 kPa for one hour,
and a reaction of a dually reactive monomer and a polyester resin
site were carried out. Further, trimellitic anhydride, fumaric
acid, and a polymerization inhibitor were added thereto at
210.degree. C., and a reaction was carried out until a softening
point reached a value as listed in Table 1, to provide a composite
resin having the physical properties as listed in Table 1.
Production Example 5 of Resin [Resin G]
A 10-L four-neck flask equipped with a nitrogen inlet tube, a
dehydration tube, a stirrer, and a thermocouple was charged with
raw material monomers for a polyester resin other than trimellitic
anhydride and an esterification catalyst as listed in Table 1. The
contents were heated with a mantle heater to 230.degree. C., and
then reacted at 230.degree. C. for 8 hours, and further reduced
pressure to 8.3 kPa and reacted thereat for one hour. The
temperature of the reaction mixture was lowered to 170.degree. C.,
and raw material monomers for a styrenic resin, a dually reactive
monomer, and a polymerization initiator as listed in Table 1 were
added dropwise from a dropping funnel over one hour. While holding
the temperature at 170.degree. C., the addition polymerization
reaction was aged for one hour. Thereafter, the reaction mixture
was heated to 210.degree. C., and subjected to removal of the raw
material monomers for the styrenic resin at 8.3 kPa for one hour,
and a reaction of a dually reactive monomer and a polyester resin
site were carried out. Further, trimellitic anhydride was added
thereto at 210.degree. C., and a reaction was carried out until a
softening point reached a value as listed in Table 1, to provide a
composite resin having the physical properties as listed in Table
1.
TABLE-US-00001 TABLE 1 Resin A Resin B Resin C Resin D Resin E
Resin F Resin G Raw Material Monomers 1,2-Propanediol 3,640 g 3,083
g -- -- -- -- -- for Polyester Resin (100) (100) BPA-PO.sup.1) --
-- 7,702 g 7,437 g 4,313 g 3,357 g 4,046 g (100) (100) (60) (50)
(70) BPA-EO.sup.2) -- -- -- -- 2,670 g 3,117 g l,610 g (40) (50)
(30) Terephthalic acid 6,360 g 5,387 g -- -- 2,898 g 2,101 g 1,288
g (80) (80) (85) (66) (47) Fumaric acid -- -- 2,298 g 2,563 g -- 89
g -- (90) (104) (4) Dodecenylsuccinic anhydride -- -- -- -- -- --
791 g (18) Trimellitic anhydride -- 530 g -- -- 118 g 295 g 729 g
(7) (3) (8) (23) Dually Reactive Monomer Acrylic acid -- -- -- --
-- 41 g 36 g (3) (3) Esterification Catalyst Tin(II)
2-ethylhexanoate 50 g 50 g 50 g 50 g 50 g 45 g 45 g Raw Material
Monomers Styrene -- -- -- -- -- 749 g 1,112 g for Styrenic Resin
(84) (84) 2-Ethylhexyl acrylate -- -- -- -- -- 143 g 212 g (16)
(16) Polymerization Initiator Dibutyl peroxide -- -- -- -- -- 54 g
79 g Polymerization Inhibitor 4-t-Butyl catechol -- -- 5 g 5 g -- 5
g -- Polyester Resin/Styrenic Resin (Mass Ratio) -- -- -- -- --
90/10 85/15 Physical Properties of Softening Point, .degree. C. 87
95 84 101 101 90 113 Resin Glass Transition Temp., .degree. C. 47
55 46 57 61 50 58 Acid Value, mgKOH/g 10 30 20 19 12 18 26 Note)
The numerical figures inside the parentheses in the raw material
monomers for a polyester resin and the dually reactive monomer are
expressed by a molar ratio when a total number of moles of the
alcohol component is defined as 100. The numerical figures inside
the parentheses in the raw material monomers for a styrenic resin
are expressed by a mass ratio when a total mass of the raw material
monomers for a styrenic resin is defined as 100.
.sup.1)Polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane
.sup.2)Polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane
Production Example 1 of Dispersants [Dispersants A to G]
A 2 L four-neck flask equipped with a reflux condenser, a nitrogen
inlet tube, a stirrer, a dehydration tube, and a thermocouple was
charged with raw materials for a basic nitrogen-containing group,
raw materials for a dispersible group (maleic anhydride-modified
polypropylene (PPSA)), and xylene manufactured by Wako Pure
Chemical Industries, Ltd., and the internal of the reaction vessel
was replaced with nitrogen gas. Thereafter, the internal of the
reaction vessel was heated to 150.degree. C., and the temperature
was held thereat for one hour. Thereafter, the internal was heated
to 160.degree. C., and the temperature was held thereat for one
hour. The pressure was reduced to 8.3 kPa at 160.degree. C. to
distill off the solvent. The time point at which a peak of acid
anhydride ascribed to PPSA (1,780 cm.sup.-1) disappears and a peak
ascribed to imide bond (1,700 cm.sup.-1) is generated according to
the IR analysis is defined as a reaction end point, to provide each
of dispersants having physical properties shown in Table 2.
Production Example 2 of [Dispersants H to K]
A 2 L four-neck flask equipped with a reflux condenser, a nitrogen
inlet tube, a stirrer, a dehydration tube, and a thermocouple was
charged with raw materials for a basic nitrogen-containing group,
raw materials for a dispersible group (halogenated alkane), fine
potassium carbonate powder manufactured by Wako Pure Chemical
Industries, Ltd., and Acetonitrile, Super Dehydrated, manufactured
by Wako Pure Chemical Industries, Ltd., and the internal of the
reaction vessel was replaced with nitrogen gas. Thereafter, the
internal of the reaction vessel was heated to 80.degree. C., and
the temperature was held thereat for 200 hour. Thereafter, the
pressure was reduced to distill off the solvent. According to the
residual proportion of the proton peaks of the primary and
secondary amines of the polyethyleneimine according to NMR
analysis, the reaction percentage was confirmed to be 95% or more,
to provide each of dispersants having physical properties shown in
Table 2.
Production Example 3 of Dispersant [Dispersant L]
A 1 L four-neck flask equipped with a reflux condenser, a nitrogen
inlet tube, a stirrer, and a thermocouple was charged with 50 g of
a reaction solvent xylene, and the internal of the reaction vessel
was replaced with nitrogen gas. Thereafter, the internal of the
reaction vessel was heated to 110.degree. C., and a mixture of raw
material monomers, a polymerization initiator, and 50 g of xylene
as listed in Table 3 was added dropwise over 2 hours to carry out a
polymerization reaction. After the termination of the dropwise
addition, the reaction mixture was reacted at 110.degree. C. for
additional 3 hours. The solvent was distilled off at 110.degree.
C., to provide a dispersant composed of a copolymer having physical
properties shown in Table 3.
TABLE-US-00002 TABLE 2 Disper- Disper- Disper- Disper- Disper-
Disper- Disper- Disper- Disper- D- isper- Disper- sant A sant B
sant C sant D sant E sant F sant G sant H sant I sant J sant K Raw
Polyethyleneimine 7 -- -- -- -- -- -- -- -- -- -- Materials
(PEI)300 for Basic Polyethyleneimine -- 9 -- -- -- -- -- -- -- --
-- Nitrogen- (PEI)600 Containing Polyethyleneimine -- -- 9 -- 4 1.3
-- 20 20 20 20 Group.sup.1) (PEI)1200 Polyethyleneimine -- -- --
1.3 -- -- -- -- -- -- -- (PEI)10000 TEP -- -- -- -- -- -- 0.8 -- --
-- -- Number-Average 1,500 2,500 3,400 12,000 3,400 3,400 189 3,400
3,400 3,400- 3,400 Molecular Weight Mn Raw PPSA1000 66.2 63 59.9
65.5 -- -- 67.7 -- -- -- -- Materials PPSA2500 -- -- -- -- 66.5 --
-- -- -- -- -- for PPSA8000 -- -- -- -- -- 69.2 -- -- -- -- --
Dispersible C12-Cl -- -- -- -- -- -- -- 71 -- -- -- Group .sup.2)
C16-Cl -- -- -- -- -- -- -- -- 104 -- -- C18-Cl -- -- -- -- -- --
-- -- -- 115 -- C22-Cl -- -- -- -- -- -- -- -- -- -- 138
Number-Average 1,000 1,000 1,000 1,000 2,500 8,000 1,000 -- -- --
-- Molecular Weight Mn Solvent Xylene 73.2 72 68.9 66.8 70.5 70.5
68.5 -- -- -- -- Ultradehydrated -- -- -- -- -- -- -- 145 179 190
212 Acetonitrile Neutralizing Potassium Carbonate -- -- -- -- -- --
-- 55 55 55 55 Agent Physical Melting Point, .degree. C. 90 92 97
103 117 142 92 -8 34 50 66 Properties Note) The amount used is in
mass ratio. .sup.1)Polyethyleneimine 300, 600, 1200, and 10000: all
are manufactured by JUNSEI CHEMICAL CO., LTD., TEP:
tetraethylenepentamine: manufactured by KANTO CHEMICAL CO., INC.
.sup.2) PPSA1000: X-10065 manufactured by Baker Hughes, mp:
108.degree. C. PPSA2500: X-10088 manufactured by Baker Hughes, mp:
132.degree. C. PPSA8000: X-10082 manufactured by Baker Hughes, mp:
155.degree. C. C12-Cl: 1-chlorodecane, manufactured by TCI C16-Cl:
1-chlorohexadecane, manufactured by TCI C18-Cl: 1-chlorooctadecane,
manufactured by TCI C22-Cl: 1-chlorodocosadecane, manufactured by
TCI
TABLE-US-00003 TABLE 3 Dispersant L Raw Material
2-(Dimethylamino)ethyl 20 g Monomers methacrylate (DMAEMA)
Octadecyl methacrylate 80 g (SMA) Polymerization V-65 10 g
Initiator Solvent Xylene 50 g + 50 g Physical Weight-Average
Molecular 7,800 Properties Weight Melting Point, .degree. C. 29
2-(Dimethylamino)ethyl methacrylate: manufactured by Wako Pure
Chemical Industries, Ltd. Octadecyl methacrylate: manufactured by
Wako Pure Chemical Industries, Ltd. V-65:
2,2'-azobis(2,4-dimethylvaloronitrile), manufactured by Wako Pure
Chemical Industries, Ltd.
EXAMPLES 1 TO 11 AND COMPARATIVE EXAMPLES 1 TO 4
[Preparation of Dispersion of Resin Particles (Emulsion-Phase
Inversion Step)]
A 2 L vessel equipped with a stirrer, a reflux condenser, and a
thermometer was charged with 300 g of a resin D and 300 g of methyl
ethyl ketone. The contents were heated to 60.degree. C. while
stirring, and the temperature was held at 60.degree. C. over 30
minutes to dissolve the resin. The solution obtained was cooled to
30.degree. C., 5.1 g of a 25% by mass aqueous ammonia solution was
added thereto, and the temperature was held at 30.degree. C. for 30
minutes.
Next, with holding the temperature at 30.degree. C., 712 g of
deionized water was added over 60 minutes while stirring at 200
r/min (peripheral speed: 63 m/min) to allow emulsion
phase-inversion. The emulsified mixture was heated to 60.degree.
C., and methyl ethyl ketone was distilled off under a reduced
pressure, to provide an aqueous dispersion. Thereafter, the aqueous
dispersion was cooled to 30.degree. C., while stirring at 200 r/min
(peripheral speed: 63 m/min), and deionized water was then added so
as to have a solid content concentration of 20% by mass, to thereby
provide a dispersion of resin particles of a resin D having
physical properties shown in Table 4.
[Preparation of Dispersion of Colorant Particles]
In a 1-L beaker were mixed 150 g of a colorant "ECB-301"
manufactured by DAINICHISEIKA COLOR & CHEMICALS MFG. CO., LTD.,
Phthalocyanine Blue 15:3, 200 g of an anionic surfactant
"NEOPELEX(registered trademark) G-15," manufactured by KAO
Corporation (15% by mass aqueous sodium dodecylbenzenesulfonate),
and 257 g of deionized water, and the mixture was dispersed at room
temperature (25.degree. C.) for 3 hours with a ultrasonic
homogenizer "US-600T" manufactured by NIHONSEIKI KAISHA, LTD.
Thereafter, deionized water was added to the dispersion so as to
have a solid content concentration of 24% by mass, to thereby
provide a colorant dispersion. The volume-median particle size
D.sub.50 of the colorant particles in the dispersion was 0.10
.mu.m.
[Preparation of Toner Particles]
In a 3-L four-neck flask equipped with a dehydration tube, a
stirring device, and a thermocouple were mixed 300 g of a
dispersion of resin particles, 45 g of a dispersion of colorant
particles, and 9 g of a 10% by mass aqueous solution of a nonionic
surfactant "EMULGEN(registered trademark) 150" manufactured by KAO
Corporation (polyoxyethylene(average number of moles added: 50)
lauryl ether) at 25.degree. C. Next, while stirring the mixture, a
solution adjusted to a pH of 8.5 by adding 10 g of a 4.8% by mass
aqueous potassium hydroxide solution to an aqueous solution of 8 g
of ammonium sulfate dissolved in 180 g of deionized water was added
dropwise to the mixture at 25.degree. C. over 5 minutes.
Thereafter, the contents were heated to 65.degree. C. over 3 hours,
and the temperature was held at 65.degree. C. until a volume-median
particle size D.sub.50 of the aggregated particles became 2.5
.mu.m, to provide a dispersion of aggregated particles.
To the dispersion of aggregated particles was added an aqueous
solution prepared by mixing 10 g of an anionic surfactant
"EMAL(registered trademark) E-27C" manufactured by KAO Corporation,
sodium polyoxyethylene lauryl ether sulfate, effective
concentration: 27% by mass, 900 g of deionized water, and 30 g of
0.1 mol/L sulfuric acid. Thereafter, contents were heated to
85.degree. C. over 1 hour, and the temperature was held at
85.degree. C. until a circularity reached a value of 0.985, to
thereby provide a dispersion of unified particles in which the
aggregated particles were fused.
The dispersion of unified particles obtained was cooled to
30.degree. C., the dispersion was subjected to suction filtration
to separate a solid content, and the residues were washed with
deionized water at 25.degree. C., and then subjected to suction
filtration at 25.degree. C. for 2 hours. Thereafter, the solids
were vacuum-dried at 40.degree. C. for 48 hours with a vacuum oven
dryer DRV622DA, manufactured by ADVANTEC, to provide toner
particles having physical properties shown in Table 4.
[Preparation of Liquid Developer]
Fifty parts by mass of toner particles and 5 parts by mass of a
dispersant as listed in Table 5 were added to 102 parts by mass of
an insulating liquid as listed in Table 5, and the mixture was
stirred with a homogenizing mixer T18 digital ULTRA-TURRAX
manufactured by IKA at 25.degree. C. for 10 minutes at 10,000
r/min. The solid content concentration was diluted to 25% by mass,
to provide a liquid developer having physical properties shown in
Table 5.
EXAMPLES 12 TO 14
The same procedures as in Example 3 were carried out except that
the resin A or the resin C was urethane-modified according to the
following method, to prepare a dispersion of resin particles, and
used, to provide each of the liquid developers having physical
properties shown in Tables 5 and 6.
[Preparation of Dispersion of Resin Particles]
<Urethane Stretching Step>
A 2 L vessel equipped with a stirrer, a reflux condenser, a
thermometer, and a nitrogen inlet tube was charged with 200 g of a
resin as listed in Table 4, and methyl ethyl ketone,
dimethylolbutanoic acid, and tin(II) 2-ethylhexanoate each as
listed in Table 4, which were previously subjected to a dehydration
treatment with molecular sieves, under a nitrogen atmosphere. The
contents were heated to 80.degree. C. while stirring, and the
temperature was held at 80.degree. C. over 30 minutes to dissolve
the resin. Hexamethylene diisocyanate as listed in Table 4 was
added to the solution obtained, and the temperature was held at
80.degree. C. for 5 hours, to provide a methyl ethyl ketone
solution of a urethane-modified polyester resin.
<Emulsion Phase-Inversion Step>
Next, the solution obtained was cooled to 30.degree. C., methyl
ethyl ketone and a 25% by mass aqueous ammonia solution as listed
in Table 4 were added thereto, and the temperature was held for 30
minutes while stirring. Next, with holding the temperature at
30.degree. C., deionized water as listed in Table 4 was added
thereto over 60 minutes while stirring at 200 r/min (peripheral
speed: 63 m/min) to cause emulsion phase-inversion. The internal
was heated to 60.degree. C., and methyl ethyl ketone was distilled
off under a reduced pressure, to provide an aqueous dispersion.
Thereafter, the aqueous dispersion was cooled to 30.degree. C.,
while stirring at 200 r/min (peripheral speed: 63 m/min), and
deionized water was then added thereto so as to have a solid
content concentration of 20% by mass, to thereby provide a
dispersion of resin particles having physical properties shown in
Table 4.
TABLE-US-00004 TABLE 4 Exs. 1 to 11 Comp. Exs. Exs. 12 1 to 4 and
13 Ex. 14 Resin Resin D Resin A Resin C 300 g 200 g 200 g Urethane
Dimethylolbutanoic acid -- 11.3 g 4.6 g stretching step Methyl
ethyl ketone -- 186 g 171 g Tin(II) 2-ethylhexanoate -- 1 g 1 g
Hexamethylene diisocyanate -- 36.3 g 22.8 g Emulsion 25% by Mass
aqueous ammonia 5.1 g 4.5 g 5.9 g phase-inversion Methyl ethyl
ketone 300 g 195 g 198 g step Deionized water 712 g 578 g 531 g
Dispersion of PH 6.8 6.9 6.7 resin particles Physical Volume-median
particle size, nm 100 160 90 properties of CV value, % 20 26 18
resin particles Glass transition temperature, .degree. C. 57 70 62
Softening point, .degree. C. 100 126 118 Physical Volume-median
particle size, nm 2.5 2.5 2.4 properties of CV value, % 19 20 21
toner particles Glass transition temperature, .degree. C. 46 59 52
Softening point, .degree. C. 95 107 101
EXAMPLES 15 TO 20
[Preparation of Toner Particles]
Eighty-five parts by mass of a resin binder as listed in Table 6
and 15 parts by mass of a colorant "ECB-301" manufactured by
DAINICHISEIKA COLOR & CHEMICALS MEG. CO., LTD., Phthalocyanine
Blue 15:3, were previously stirred with a 20-L Henschel mixer for 3
minutes at a rotational speed of 1,500 r/min (peripheral speed 21.6
m/sec), and the mixture was melt-kneaded under the conditions given
below.
[Melt-Kneading Conditions]
A continuous twin open-roller type kneader "Kneadex," manufactured
by NIPPON COKE & ENGINEERING CO., LTD. having an outer diameter
of roller of 14 cm and an effective length of roller of 55 cm was
used. The operating conditions of the continuous twin open-roller
type kneader were a peripheral speed of a high-rotation roller
(front roller) of 75 r/min (32.4 m/min), a peripheral speed of a
low-rotation roller (back roller) of 35 r/min (15.0 m/min), and a
gap between the rollers at an end of the kneaded product supplying
side of 0.1 mm. The temperatures of the heating medium and the
cooling medium inside the rollers were as follows.
The high-rotation roller had a temperature at the raw material
supplying side of 90.degree. C., and a temperature at the kneaded
product-discharging side of 85.degree. C., and the low-rotation
roller had a temperature at the raw material supplying side of
35.degree. C., and a temperature at the kneaded product-discharging
side of 35.degree. C. In addition, the feeding rate of the raw
material mixture to the kneader was 10 kg/h, and the average
residence time in the kneader was about 3 minutes.
The kneaded product obtained above was roll-cooled with a cooling
roller, and the cooled product was roughly pulverized with a
hammer-mill to a size of 1 mm or so, and then finely pulverized and
classified with an air jet type jet mill "IDS," manufactured by
Nippon Pneumatic Mfg. Co., Ltd., to provide toner particles having
a volume-median particle size D.sub.50 of 10 .mu.m.
[Preparation of Liquid Developer]
A 2-L polyethylene vessel was charged with 100 g of toner
particles, 204 g of an insulating liquid as listed in Table 6, and
10 g of a dispersant C, and the contents were stirred with "T.K.
ROBOMIX," manufactured by PRIMIX Corporation, under ice-cooling at
a rotational speed of 7,000 r/min for 30 minutes, to provide a
dispersion of toner particles, a solid content concentration of
which was 35% by mass.
Next, the dispersion of toner particles obtained was subjected to
wet-milling for 4 hours with 6 vessels-type sand grinder "TSG-6,"
manufactured by AIMEX CO., LTD., at a rotational speed of 1,300
r/min (peripheral speed 4.8 msec) using zirconia beads having a
diameter of 0.8 mm at a volume filling ratio of 60% by volume. The
beads were removed by filtration, and the filtrate was diluted with
the insulating liquid, to provide a liquid developer, a solid
content concentration of which was 25% by mass, the liquid
developer having physical properties as shown in Table 6.
EXAMPLE 21
[Preparation of Toner Particles]
Eighty-five parts by mass of a resin D, 15 parts by mass of a
colorant "ECB-301" manufactured by DAINICHISEIKA COLOR &
CHEMICALS MFG. CO., LTD., Phthalocyanine Blue 15:3, and 10 parts by
mass of a dispersant C were previously mixed with a 20-L Henschel
mixer while stirring for 3 minutes at a rotational speed of 1,500
r/min (peripheral speed 21.6 m/sec). Thereafter, the melt-kneading,
the pulverization, and the classification were carried out in the
same manner as in Example 13, to provide toner particles.
[Preparation of Liquid Developer]
A 2-L polyethylene vessel was charged with 100 g of the toner
particles obtained and 186 g of an insulating liquid as listed in
Table 6, and the contents were stirred with "T.K. ROBOMIX,"
manufactured by PRIMIX Corporation, under ice-cooling at a
rotational speed of 7,000 r/min for 30 minutes, to provide a
dispersion of toner particles, a solid content concentration of
which was 35% by mass.
Next, the dispersion of toner particles obtained was subjected to
wet-milling for 4 hours with 6 vessels-type sand grinder "TSG-6,"
manufactured by AIMEX CO., LTD., at a rotational speed of 1,300
r/min (peripheral speed 4.8 m/sec) using zirconia beads having a
diameter of 0.8 mm at a volume filling ratio of 60% by volume. The
beads were removed by filtration, and the filtrate was diluted with
the insulating liquid, to provide a liquid developer, a solid
content concentration of which was 25% by mass, the liquid
developer having physical properties as shown in Table 6.
Test Example (Fusing Ability to Resin Film)
A liquid developer was added dropwise to an untreated surface of
each of the resin films given hereinbelow, and a thin film was
produced with a wire bar so that the mass on dry basis would be 1.2
g/m.sup.2. Thereafter, the produced thin film was held in a
thermostat at 80.degree. C. for 3 minutes to fuse.
[Resin Film] PET: "LUMIRROR T60 #75" manufactured by TORAY
INDUSTRIES, LTD. PP: "FOR25" manufactured by FUTAMURA CHEMICAL CO.,
LTD. Nylon: "EMBLEM ON-25" manufactured by UNITICA LTD.
The fused images obtained were adhered to a mending tape "Scotch
Mending Tape 810," manufactured by 3M, width of 18 mm, the tape was
pressed with a roller so as to apply a load of 500 g thereto, and
the tape was then removed. The optical densities before and after
tape removal were measured with a colorimeter "GretagMacbeth
Spectroeye," manufactured by Gretag. The fused image-printed
portions were measured at 3 points each, and an average thereof was
calculated as an optical density. A fusing ratio (%) was calculated
from a value of: [optical density after removal]/[optical density
before removal].times.100. The results are shown in Tables 5 and 6.
The larger the numerical value of the fusing ratio, the more
excellent the fusing ability.
TABLE-US-00005 TABLE 5 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7
Toner Resin Binder Resin D Resin D Resin D Resin D Resin D Resin D
Resin D Insulating Insulating Liquid Isopar L Isopar L Isopar L
Isopar L Isopar L Isopar L Isopar L Liquid Viscosity, mPa s 1.0 1.0
1.0 1.0 1.0 1.0 1.0 Dispersant Dispersant Disper- Disper- Disper-
Disper- Disper- Disper- Disp- er- sant A sant B sant C sant D sant
E sant F sant G Raw Materials for PEI PEI PEI PEI PEI PEI TEP Basic
Nitrogen- 300 600 1200 10000 1200 1200 Containing Group Mn of Raw
Materials 1,500 2,500 3,400 12,000 3,400 3,400 189 for Basic
Nitrogen- Containing Group Raw Materials for PPSA PPSA PPSA PPSA
PPSA PPSA PPSA Dispersible Group 1000 1000 1000 1000 2500 8000 1000
Mn of Raw Materials 1,000 1,000 1,000 1,000 2,500 8,000 1,000 for
Dispersible Group Melting Point, .degree. C. 90 92 97 103 117 142
92 Physical D.sub.50, .mu.m 2.2 2.2 2.4 2.5 2.5 2.5 2.1 Properties
of Viscosity, mPa s 2 2 2 3 3 5 5 Liquid Developer Evaluations PET
Fusing Ratio, % 100 100 100 100 100 100 100 for Fusing PP Fusing
Ratio, % 91 95 100 100 97 93 90 Nylon Fusing Ratio, % 35 24 15 9 10
11 25 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Toner Resin Binder
Resin D Resin D Resin D Resin D Urethane- Urethane- Modified
Modified Resin A Resin A Insulating Insulating Liquid Isopar L
Isopar L Isopar L NAS-3 Isopar L NAS-3 Liquid Viscosity, mPa s 1.0
1.0 1.0 1.0 1.0 1.0 Dispersant Dispersant Disper- Disper- Disper-
Disper- Disper- Disper- sant I sant J sant K sant C sant C sant C
Raw Materials for PEI PEI PEI PEI PEI PEI Basic Nitrogen- 1200 1200
1200 1200 1200 1200 Containing Group Mn of Raw Materials 3,400
3,400 3,400 3,400 3,400 3,400 for Basic Nitrogen- Containing Group
Raw Materials for C16-Cl C18-Cl C22-Cl PPSA PPSA PPSA Dispersible
Group 1000 1000 1000 Mn of Raw Materials -- -- -- 1,000 1,000 1,000
for Dispersible Group Melting Point, .degree. C. 34 50 66 97 97 97
Physical D.sub.50, .mu.m 2.2 2.5 3.0 2.4 2.5 2.4 Properties of
Viscosity, mPa s 2 2 10 2 3 2 Liquid Developer Evaluations PET
Fusing Ratio, % 92 95 98 100 100 100 for Fusing PP Fusing Ratio, %
5 10 15 100 100 100 Nylon Fusing Ratio, % 21 16 9 45 98 100 Note)
Isopar L: manufactured by Exxon Mobile Corporation, isoparaffin,
conductivity: 6.2 .times. 10.sup.-13 S/m, viscosity at 25.degree.
C.: 1 mPa s, boiling point: 203.degree. C. NAS-3: manufactured by
NOF, polyisobutene, conductivity: 1.68 .times. 10.sup.-12 S/m,
viscosity at 25.degree. C.: 1 mPa s, boiling point: 168.degree.
C.
TABLE-US-00006 TABLE 6 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex. 19
Ex. 20 Toner Resin Binder Urethane- Resin D Resin B Resin B Resin
F/ Resin E Resin E Modified Resin G = Resin C 50/50, Mass Ratio
Insulating Insulating Liquid Isopar L Isopar L Isopar L NAS-3
Isopar L Isopar L NAS-3 Liquid.sup.1) Viscosity, mPa s 1.0 1.0 1.0
1.0 1.0 1.0 1.0 Dispersant.sup.2) Dispersant Disper- Disper-
Disper- Disper- Disper- Dispe- r- Disper- sant C sant C sant C sant
C sant C sant C sant C Raw Materials for PEI PEI PEI PEI PEI PEI
PEI Basic Nitrogen- 1200 1200 1200 1200 1200 1200 1200 Containing
Group Mn of Raw Materials 3,400 3,400 3,400 3,400 3,400 3,400 3,400
for Basic Nitrogen- Containing Group Raw Materials for PPSA PPSA
PPSA PPSA PPSA PPSA PPSA Dispersible Group 1000 1000 1000 1000 1000
1000 1000 Mn of Raw Materials 1,000 1,000 1,000 1,000 1,000 1,000
1,000 for Dispersible Group Melting Point, .degree. C. 97 97 97 97
97 97 97 Physical D.sub.50, .mu.m 2.4 2.5 2.2 1.8 2.0 2.6 1.5
Properties Viscosity, mPa s 3 3 3 2 3 5 3 of Liquid Developer
Evaluations PET Fusing Ratio, % 100 100 100 100 100 100 100 for
Fusing PP Fusing Ratio, % 100 100 100 100 100 100 100 Nylon Fusing
Ratio, % 92 78 85 90 9 68 73 Comp. Comp. Comp. Comp. Ex. 21 Ex. 1
Ex. 2 Ex. 3 Ex. 4 Toner Resin Binder Resin D Resin D Resin D Resin
D Resin D Insulating Insulating Liquid Isopar L Isopar L Isopar L
Isopar L Isopar L Liquid.sup.1) Viscosity, mPa s 1.0 1.0 1.0 1.0
1.0 Dispersant.sup.2) Dispersant Disper- Disper- S11200 Disper-
V-220 sant C sant H sant L Raw Materials for PEI PEI PEI DMAEMA
Vinyl Basic Nitrogen- 1200 1200 (tertiary pyrrolidone Containing
Group amine) (amide) Mn of Raw Materials 3,400 3,400 -- -- -- for
Basic Nitrogen- Containing Group Raw Materials for PPSA C12-Cl
p-HSA SMA Eicosene Dispersible Group 1000 (C18) (C20) Mn of Raw
Materials 1,000 -- -- -- -- for Dispersible Group Melting Point,
.degree. C. 97 -8 -17 29 49 Physical D.sub.50, .mu.m 1.8 5.2 2.5
2.1 4.5 Properties Viscosity, mPa s 2 3 3 3 25 of Liquid Developer
Evaluations PET Fusing Ratio, % 100 74 23 85 82 for Fusing PP
Fusing Ratio, % 100 4 3 12 15 Nylon Fusing Ratio, % 85 25 4 6 6
.sup.1)Isopar L: manufactured by Exxon Mobile Corporation,
isoparaffin, conductivity: 6.2 .times. 10.sup.-13 S/m, viscosity at
25.degree. C.: 1 mPa s, boiling point: 203.degree. C. NAS-3:
manufactured by NOF, polyisobutene, conductivity: 1.68 .times.
10.sup.-12 S/m, viscosity at 25.degree. C.: 1 mPa s, boiling point:
168.degree. C. .sup.2)S11200 (SOLSPARSE 11200): manufactured by
Lubrizol Corporation, a condensate of a polyimine
(polyethyleneimine) and a carboxylic acid (12-hydroxystearic acid
(p-HSA), average degree of polymerization: 7.0, effective content:
50% by mass, weight-average molecular weight: 10,400,
polyimine/carboxylic acid (mass ratio) = 7/93, melting point:
-17.degree. C. V-220 (Antaron V-220): (eicosene/vinyl pyrrolidone)
copolymer, melting point: 49.degree. C.
It can be seen from the above results that the liquid developers of
Examples 1 to 21 are excellent in fusing even on an untreated resin
film.
On the other hand, the liquid developers of Comparative Examples 1
to 3 where the melting points of the dispersants are low and the
liquid developer of Comparative Example 4 where the dispersant has
an amide group are deficient in fusing ability to a resin film.
The liquid developer of the present invention is suitably used in
development or the like of latent images formed in, for example,
electrophotography, electrostatic recording method, electrostatic
printing method or the like.
* * * * *